Fluffernutter Bars

Fluffernutter Bars bring together two classic flavors in one soft, chewy dessert: creamy peanut butter and sweet marshmallow fluff. The peanut butter gives the bars a rich, slightly salty flavor, while the marshmallow layer adds a light, gooey sweetness that makes every bite feel indulgent.

The batter is simple to mix with everyday baking ingredients, and the finished bars have a tender, dense texture rather than the crisp edges you might expect from cookies. They’re especially good when you want a peanut butter dessert that can be baked in a pan, sliced into portions, and shared without the fuss of individual cookies.

Why You’ll Love This Recipe

• Peanut butter is the star. With 1½ cups of smooth peanut butter in the batter, these bars have plenty of rich peanut butter flavor throughout.
• Marshmallow fluff adds a soft, sweet contrast. The creamy marshmallow layer balances the deeper flavor of the peanut butter.
• The texture is soft and chewy. Brown sugar, butter, and an extra egg yolk help create a tender bar with a satisfying bite.
• No complicated decorating is needed. The marshmallow fluff provides the finishing layer, so there’s no separate frosting to prepare.
• They’re easy to portion. Once cooled, the bars can be cut into squares or rectangles, making them convenient for serving and sharing.

Preparation and Tools

Before starting, soften the unsalted butter so it can cream smoothly with the sugars. Cold butter can leave the batter uneven and make it harder to incorporate the sugar properly.

A large mixing bowl and an electric hand mixer or stand mixer are useful for combining the butter, sugars, peanut butter, egg, and egg yolk. You’ll also need a separate bowl for the dry ingredients and a spatula for folding and spreading the thick batter.

A baking pan lined with parchment paper is particularly helpful. The peanut butter batter is fairly thick, so parchment makes it easier to remove the cooled bars from the pan before slicing.

Preparation Tips

Use smooth peanut butter. Smooth peanut butter gives these bars their characteristic creamy texture. Since the recipe specifically calls for smooth peanut butter, avoid switching to chunky peanut butter unless you want pieces of peanuts throughout the bars.

Soften the butter properly. The butter should be soft enough to mix easily but not melted. Melted butter changes the consistency of the batter and can affect the final texture.

Separate the egg yolk carefully. The recipe uses one whole egg plus an additional yolk. The extra yolk contributes richness without adding another egg white, which helps keep the bars tender.

Measure the flour carefully. Too much flour can make peanut butter bars dense and dry. For the most consistent result, spoon the flour into a measuring cup and level it rather than packing it down.

Handle the marshmallow fluff gently. Marshmallow fluff is sticky and can be difficult to spread. A lightly greased spatula can make the job easier and help you distribute it without pulling up too much of the batter underneath.

Ingredients

All-Purpose Flour

Flour provides the structure for the bars. Measuring it accurately is important because the batter needs enough structure to support the marshmallow fluff while remaining soft after baking.

Baking Powder and Salt

Baking powder provides the lift needed for the bars, while a small amount of salt balances the sweetness and complements the peanut butter.

Unsalted Butter

Softened butter contributes richness and helps create the tender texture of the finished bars. Using unsalted butter also gives you better control over the amount of salt in the recipe.

Brown Sugar and White Sugar

The combination of brown sugar and white sugar gives the bars both sweetness and a deeper caramel-like flavor. Brown sugar also helps maintain the soft texture that makes these bars especially enjoyable.

Smooth Peanut Butter

Peanut butter is the defining ingredient here. The generous amount gives the bars a pronounced peanut butter flavor and contributes richness to the batter.

Egg and Egg Yolk

One whole egg provides structure and moisture, while the additional yolk adds richness and helps keep the bars tender.

Marshmallow Fluff

The marshmallow fluff creates the signature second flavor in these bars. Its airy, sweet character works especially well against the rich peanut butter base.

Cooking Instructions

Step 1: Prepare the Baking Pan

Preheat the oven to the temperature specified by your baking setup and prepare the baking pan with parchment paper, leaving some parchment extending over the sides if possible. This will make the baked bars much easier to lift out later.

Make sure the pan is prepared before mixing the batter because the finished mixture will be thick and is best transferred to the pan soon after it is combined.

Step 2: Combine the Dry Ingredients

In a medium bowl, whisk together the all-purpose flour, baking powder, and salt.

Mixing these ingredients separately helps distribute the baking powder and salt evenly throughout the flour. Set the bowl aside while you prepare the peanut butter mixture.

Step 3: Cream the Butter and Sugars

In a large mixing bowl, beat the softened unsalted butter with the brown sugar and white sugar until the mixture is smooth and well combined.

Take your time during this step and scrape down the sides of the bowl as needed. The goal is to evenly incorporate the butter and sugars before adding the remaining wet ingredients.

Step 4: Add the Peanut Butter and Eggs

Add the smooth peanut butter to the butter-and-sugar mixture and beat until evenly combined.

Add the large egg and the additional egg yolk, making sure the egg white from the second egg has been discarded. Mix until the batter is smooth and the ingredients are fully incorporated.

The mixture should look thick, creamy, and evenly blended, with no visible streaks of plain butter or peanut butter.

Step 5: Add the Dry Ingredients

Gradually add the flour mixture to the peanut butter mixture. Mix just until the dry ingredients are incorporated.

Avoid overmixing once the flour has disappeared. Because this is a bar cookie-style batter, excessive mixing can make the finished texture less tender.

The batter will be thick, so don’t expect it to have the loose consistency of cake batter.

Step 6: Spread the Batter in the Pan

Transfer the peanut butter batter to the prepared baking pan. Use a spatula to spread it into an even layer, working gently to reach the corners.

Because the batter is thick, spreading it evenly is more important than trying to smooth it quickly. An even layer helps the bars bake consistently from edge to center.

Step 7: Add the Marshmallow Fluff

Spoon the 7-ounce jar of marshmallow fluff over the peanut butter batter and spread it into an even layer.

Work carefully because marshmallow fluff is sticky. If it begins sticking heavily to the spatula, lightly greasing the utensil can make spreading easier.

Try to distribute the fluff across the surface rather than concentrating it in one area. This ensures that the finished bars have a good balance of peanut butter and marshmallow in each portion.

Step 8: Bake Until Set

Place the pan in the preheated oven and bake according to the recipe’s baking time, watching for the appropriate visual cues.

The bars should be baked through without becoming overly dry. Since oven temperatures and pan sizes can affect baking speed, begin checking toward the end of the expected baking time.

Once baked, remove the pan from the oven and allow the bars to cool thoroughly before cutting. The cooling time is important because the marshmallow layer and soft peanut butter base need time to settle.

Step 9: Cool and Slice

Let the bars cool completely in the pan. Once they have firmed up, use the parchment overhang to lift them from the pan if desired.

Place the slab on a cutting board and slice into squares or rectangles with a sharp knife. For cleaner cuts, wipe the knife between slices, especially where the marshmallow fluff becomes sticky.

Notes

If you want especially neat portions, allow the bars to cool completely before slicing rather than cutting them while warm. The marshmallow fluff is much easier to manage once it has settled.

For easier removal, parchment paper is preferable to simply greasing the pan. Leaving an overhang on two sides creates convenient handles for lifting the cooled bars.

Because the recipe relies heavily on peanut butter and marshmallow fluff for its flavor, keep the ingredient proportions as supplied if you want the intended balance between the rich peanut butter base and sweet marshmallow topping.

Common Mistakes to Avoid

Using melted butter instead of softened butter. Melted butter changes the consistency of the mixture and can produce a different texture. Let the butter soften naturally until it is easy to beat but still holds its shape.

Adding too much flour. Over-measuring flour is an easy way to end up with dry, overly firm bars. Spoon the flour into the measuring cup and level it for a more accurate measurement.

Overmixing after adding the flour. Once the dry ingredients are incorporated, stop mixing. Continuing to beat the batter unnecessarily can make the bars tougher.

Spreading the marshmallow fluff too aggressively. Because fluff is sticky, pressing down too hard can disturb the peanut butter batter underneath. Use a gentle spreading motion and a lightly greased spatula if necessary.

Cutting the bars while they’re still hot. Warm marshmallow fluff can make slicing messy and cause the bars to lose their shape. Give them plenty of time to cool before cutting.

What to Serve With Fluffernutter Bars

Fluffernutter Bars are rich and sweet, so they pair especially well with simple drinks and lighter accompaniments rather than other heavily sweet desserts.

• Coffee: The slight bitterness of hot coffee balances the sweetness of the marshmallow fluff and brings out the roasted flavor of the peanut butter.
• Cold milk: A glass of cold milk is a natural pairing for these soft, chewy bars and helps balance their rich texture.
• Black tea: Unsweetened black tea provides enough contrast to keep the dessert from tasting overly sweet.
• Fresh berries: Strawberries, raspberries, or blueberries can add a bright, slightly tart element alongside the rich peanut butter bars.
• Vanilla ice cream: For a more indulgent dessert, serve a bar slightly warmed with a scoop of vanilla ice cream.

Because the bars are substantial on their own, they also work nicely as a simple addition to a cookie tray or dessert platter.

Storage Instructions

Allow the Fluffernutter Bars to cool completely before storing them. Once cooled, place them in an airtight container with parchment paper between layers if you need to stack them.

They can be kept at room temperature for several days in a cool, dry place. Keeping the container tightly sealed helps prevent the bars from drying out and protects the marshmallow layer from becoming excessively sticky.

For longer storage, the bars can be refrigerated in an airtight container. Bring them back toward room temperature before serving if you prefer a softer texture, since refrigeration will make the peanut butter base firmer.

The bars can also be frozen for longer-term storage. For best results, wrap individual portions tightly and place them in a freezer-safe container or bag. Thaw them in the refrigerator or at room temperature before serving. Because the marshmallow fluff can change slightly in texture after freezing and thawing, allow the bars to come fully to room temperature before judging their final texture.

If you’re preparing them ahead for an event, baking and cooling the bars a day in advance works well. Keep them properly covered until you’re ready to slice and serve.

Estimated Nutrition

Nutrition will vary depending on the exact brands of peanut butter, marshmallow fluff, butter, and other ingredients used, as well as the number of portions cut from the pan.

Estimated nutrition per serving:

• Calories: approximately 320–350
• Carbohydrates: approximately 38 g
• Protein: approximately 7 g
• Fat: approximately 17 g
• Saturated Fat: approximately 7 g
• Sugar: approximately 23 g
• Sodium: approximately 220 mg

These figures are estimates intended as a general guide rather than verified nutritional values.

Frequently Asked Questions

Can I use chunky peanut butter?

The supplied recipe calls for smooth peanut butter, which gives the bars their intended creamy texture. Chunky peanut butter can technically be used, but it will introduce pieces of peanuts throughout the bars and change their texture.

Why does the recipe use an extra egg yolk?

The additional yolk provides richness and moisture without adding another egg white. This helps support the soft, tender texture of the peanut butter bars.

Can I use melted butter?

It’s better to use softened butter as specified. Softened butter combines properly with the sugars during mixing, while melted butter changes the consistency of the batter and can affect the final texture.

How do I spread marshmallow fluff without making a mess?

Marshmallow fluff is naturally sticky, so use a spatula to gently spread it across the peanut butter batter. Lightly greasing the spatula can make the process easier. Avoid pressing down too firmly, as this can disturb the batter underneath.

Why should I wait for the bars to cool before cutting?

The peanut butter base needs time to firm up, while the marshmallow layer needs time to settle. Cutting the bars while they’re hot can make them difficult to handle and result in messy portions. Cooling completely gives you cleaner slices.

Can I make these bars ahead of time?

Yes. They can be baked and cooled ahead of serving. Once completely cool, keep them covered in an airtight container until you’re ready to serve them.

Conclusion

Fluffernutter Bars combine a rich peanut butter base with a sweet, airy marshmallow layer for a dessert that’s both simple to prepare and easy to share. The extra egg yolk helps keep the bars tender, while the brown sugar adds depth to the peanut butter flavor. Once cooled and sliced, they’re ready for everything from an afternoon treat with coffee to a spot on a dessert platter.

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