These fluffernutter bars are a nostalgic dessert; soft peanut butter cookie bars with a gooey marshmallow layer. The quick and easy dough mixes in one bowl and bakes in one pan. Made with mini marshmallows and peanut butter, they are perfect for your next party!
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As a busy mama and self taught baker, I like to make dessert bars when I don’t have a lot of time. I have been baking cookie bars for multiple decades and I love how easy they are to create. This quick recipe is like my marshmallow brownies and s’mores bars in that we layer marshmallows between the cookie dough to get the sweet and gooey marshmallow layer.
Much like my peanut butter blondies and nutter butter bars, you will love the soft and fudgy texture and the fact that the bars mix up in one bowl without a mixer. Slice them into small squares or larger bars, either way I know you will love them. And if you are more of a pb&j person, give my peanut butter and jelly cake a try!
🛒 ingredients notes
Please scroll to the printable recipe card at the end of this post for the full list of ingredients and baking directions.
- Peanut butter ~ creamy, no-stir peanut butter is best for this recipe. I recommend using a commercial brand like Jif or Skippy. If you prefer crunchy peanut butter, that can be substituted.
- Marshmallows ~ the mini version works best, but if you only have large marshmallows I would cut them into fourths so they melt more easily. A knife sprayed with cooking spray will help to keep them from sticking.
- Egg ~ one large egg is needed. While room temperature is preferred, it will not make or break the recipe if the egg is cold from the refrigerator.
Pro tip ~ to quickly bring eggs to room temperature, place them in a bowl of warm tap water for 5-10 minutes.
💭 can I use crunchy peanut butter?
Yes! Smooth or crunchy peanut butter works in this quick recipe, so use your favorite.
🥣 how to make in photos
Preheat oven to 350°F and prepare an 8x8 baking pan by lining it with parchment paper or aluminum foil. Lightly butter or grease the parchment paper making sure to get the sides.
In a medium to large bowl, whisk melted butter and peanut butter until smooth.
Then add the brown sugar, granulated sugar, baking powder and kosher salt and whisk until combined.
Add the egg and vanilla and whisk until thoroughly combined.
Add the flour and then mix into wet ingredients with a spatula until just combined. The batter is very thick.
Spread about ⅔ of the batter evenly {about 415g} into the prepared pan and bake for 15 minutes. Place the remaining dough in the refrigerator while the first part bakes.
Then remove pan from oven {but leave the oven turned on} and spread the mini marshmallows over the peanut butter layer. Use caution as the pan is hot.
Then remove the dough from the refrigerator and crumble the remaining peanut butter dough over the marshmallows.
Return the pan to oven and bake an additional 12-15 minutes, until the edges are lightly browned.
Let the bars cool sitting in the pan on a wire cooling rack. If desired, once the bars are cool, melt 1-2 tablespoons of peanut butter and drizzle over the tops of the bars.
👩🏻🍳 tips for the best success with your dessert bars
I know I am a broken record here, but measure your ingredients correctly. The spoon and level method is recommended for measuring flour, fluff the flour in its container, then spoon into a measuring cup and level it off with the flat side of a knife. For less dishes to wash, use a food scale and skip the measuring cups! This is the scale that I use and love.
Line the 8x8 baking pan with parchment paper and lightly butter or spray the sides with baking release spray. The marshmallow layer makes them sticky and you will thank me for this tip when removing them from the pan.
I lightly spray the knife with cooking spray before cutting the dessert bars. This helps to keep the marshmallow layer from sticking to the knife.
For the best peanut butter fluff bars, I recommend baking in a light colored 8x8 baking pan. Dark pans absorb more heat and can cause the edges to burn while the middle is undercooked. Glass pans also distribute the heat differently and can have similar results to dark colored baking pans. If baking in glass, it’s recommended to lower the temperature by 25°F and bake for a few minutes longer.
Remember your oven is different from mine and the baking time may be slightly different. I use this oven thermometer to ensure my oven is at the temperature I think it is.
If you need to speed up the cooling process, once the fluffernutter bars have cooled enough that you can pick up the pan with your bare hands, place the pan in the refrigerator to cool completely.
🫙 how to store
Store fluffernutter cookie bars in an airtight at room temperature for up to 5 days.
They also freeze well in an airtight container for up to three months.
Remember to snap a picture and tag me @twosugarbugs on Instagram if you make these Easy Fluffernutter Bars. It warms my heart to see you bring these recipes to life! Thank you for being here and happy baking!
If you make this recipe {or any recipe!} from two sugar bugs please come back and leave a review and a ⭐️⭐️⭐️⭐️⭐️ star rating. I read every comment, and I LOVE hearing from you!
📖 recipe
Easy Fluffernutter Bars {One Bowl}
recipe created and tested by:
I highly recommend using weight (metric) measurements when available for more accuracy and the best results.
Please note
When using 2x or 3x ingredients, the grams DO NOT adjust, you will have to manually do that.
Ingredients
- ½ cup unsalted butter melted (1 stick or 113g)
- ½ cup creamy peanut butter* 120g
- ½ cup packed dark or light brown sugar** 100g
- ⅓ cup granulated sugar 67g
- 1 teaspoon baking powder
- ½ teaspoon kosher salt
- 1 large egg room temperature preferred
- 2 teaspoons pure vanilla extract
- 1 cup all-purpose flour 125g
- 2 cups mini marshmallows 96g
Instructions
- Preheat oven to 350°F and prepare an 8x8 baking pan by lining it with parchment paper or aluminum foil. Lightly butter or grease the parchment paper making sure to get the sides. Leave a little overhang so you can easily pull the bars out to cut them.
- In a medium to large bowl, whisk melted butter (½ cup/113g) and peanut butter (½ cup/120g) until smooth. Then add the brown sugar (½ cup/100g), granulated sugar (⅓ cup/67g), baking powder (1 teaspoon) and kosher salt (½ teaspoon) and whisk until combined. Add the egg (1 large) and vanilla (2 teaspoons) and whisk until thoroughly combined.
- Add the flour (1 cup/125g) and then mix into wet ingredients with a spatula until just combined. The batter is very thick.
- Spread about ⅔ of the batter evenly (about 415g) into the prepared pan and bake for 15 minutes. Place the remaining dough in the refrigerator while the first part bakes.
- Then remove pan from oven (but leave it turned on) and spread the mini marshmallows (2 cups/96g) over the peanut butter layer. Use caution as the pan is hot. Then remove the dough from the refrigerator and crumble the remaining peanut butter dough over the marshmallows. Return the pan to oven and bake an additional 12-15 minutes, until the edges are lightly browned. Let the bars cool sitting in the pan on a wire cooling rack.
- If desired, once the bars are cool, melt 1-2 tablespoons of peanut butter and drizzle over the tops of the bars.
- Cut into desired size and enjoy!
Notes
Nutrition
The nutrition information is based on third-party calculations, is an estimate only and may not be entirely accurate. Actual nutritional values will vary based on brands used and portion sizes.
Michelle says
Can't go wrong with fluffy marshmallows in these bars! So delish!
Tasia says
Thank you Michelle, fluffy marshmallows and peanut butter were definitely made to go together!