These soft, gooey peanut butter cookie bars are made in one bowl in a 9x13" pan and deliver the perfect sweet-and-salty bite. Think of them like a peanut butter twist on a s'more in cookie bar form!
Reader review ★★★★★
"They turned out amazing!! So gooey and so much delicious flavors!"
Kind of like s'mores bars but with peanut butter 👀
These came to be after my s'more bars when mega viral on Tiktok and people were asking if they could make a peanut butter version. UMM YES, yes you can.
Here's why I love these:
- Soft & Gooey: These have a melt-in-your-mouth texture reminiscent of a gooey s'more.
- Sweet & Salty: The peanut butter mixed with the marshmallow creates a peanut-butter-lovers dream.
- Packed with mix-ins: I use chocolate chips, mini marshmallows, and mini Reeses for a triple threat of sweet & salty.
viral video
Watch me make this on Tiktok!
Watch me make this on Tiktok! You'll see how easy it is to make these peanut butter cookie bars:
what you need
Ingredient Notes & Substitutions
- Creamy peanut butter: Because they are already super soft & tender, I don't recommend using natural peanut butter as it will be too oily.
- Cornstarch: This helps give the cookie bars a softer & chewier texture but you can omit it, if needed.
- Mix-ins: Honestly, use whatever mix-ins or peanut butter cups you like best. I've done these with just the chocolate chips, or with the Reeses Miniatures or the Minis (the super tiny ones) and both are great!
How to Make These Fluffernutter Cookie Bars
These are super easy to make and can be whipped up in one bowl!
Make Dough
You can make this with a hand mixer or a stand mixer with the paddle attachment. It does start getting thick at the end, so if you're using a hand mixer, you may need to finish with a spatula.
Press into Pan & Bake
The easiest way to press thick doughs into a pan is to drop it in small chunks, then spray your hands with nonstick cooking spray, then press it into the corners.
You can add some extra peanut butter cups on top to get that iconic look!
Cut
It's easiest to let the bars cool before cutting (I put them in the fridge). Then you can lift them out of the pan with the parchment sling to cut, or leave them in the pan if you're taking them somewhere.
Storage & Freezing:
- Storage: Store in an airtight container for 2-3 days.
- Freezing: I don't love freezing things with marshmallows, as they tend to thaw a bit sticky, but you can do it if needed.
melissa's tips
Tips & Variations
- Get the unwrapped "mini" Reeses that come in a bag to make these super easy!
- Press some marshmallows on the top before baking so that they get toasty brown.
Frequently Asked Questions:
I haven't tested these with natural but probably wouldn't recommend, since they're already a soft bar that would get too soft with the extra oil from the natural peanut butter.
Yes, absolutely! If you can, I'd recommend only making a day ahead for optimal freshness.
You definitely could do a layer of marshmallow creme in the center instead of the mini marshmallows mixed-in. I haven't tried it but it sounds delicious!
Looking for more 9x13 cookie bars?
Fluffernutter Cookie Bars
Ingredients
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Instructions
- Preheat oven to 350ºF. While preheating, be sure to read tips & tricks in post for recipe success.
- In a medium-sized mixing bowl, beat the softened ½ cup unsalted butter and ¾ cup creamy peanut butter on medium speed for 20-30 seconds until combined.
- Add in the ¾ cup light brown sugar and ¼ cup granulated sugar and continue beating on medium for another 20-30 seconds until creamy. Do not over mix.
- While the mixer is on low, add in the 1 large egg, 1 egg yolk, 1 teaspoon vanilla extract, ½ teaspoon baking soda, ¼ teaspoon salt, and 1 tablespoon cornstarch. Stir until combined. Slowly add in 1 ½ cups all-purpose flour and mix until just incorporated.
- Mix in 1 cup semi-sweet chocolate chips and 1 cup mini marshmallows.
- Grease and line a 9×13 light-colored metal pan with parchment paper (I like to create a parchment sling so I can lift the bars out of the pan to cut). Spread dough into an even layer in pan.
- If desired, press on extra chocolate chips or peanut butter cups into the top.
- Bake for 16-18 minutes or until edges are lightly brown, marshmallows are lightly toasted, and the center no longer looks wet (some ovens may need more or less time). Allow the bars to cool for at least 30 minutes before cutting, as they will fall apart when warm. For the best slice, I recommend refrigerating the bars for about 1 hour before slicing.
Notes from Melissa
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These were so quick and easy to make. The peanut butter taste really comes out in the bars. The only thing mine aren’t as gooey as the picture. Maybe I should’ve added more than a cup of mini marshmallows.
They turned out amazing!! So gooey and so much delicious flavors!
So glad that you enjoyed this recipe Jean, thank you for taking the time to leave a review!