These Marshmallow Peanut Butter Chocolate Chip Cookie Bars are rich, gooey, and completely over-the-top. Filled with reeses peanut butter cups and marshmallow fluff, this dessert bar recipe is a chocolate peanut butter lovers dream dessert!

Chocolate Peanut Butter Cookie Bars could only be made better with marshmallow fluff! It makes for such an easy yet gooey dessert recipe.

I think we could all use some over-the-top, amazingly rich, cookie bars.

It’s been a tough beginning to 2020 and this month has felt like it will absolutely never end.

When I need a comfort food dessert, the first thing that comes to mind is chocolate and peanut butter. It’s such a rich combination, yet there’s something so comforting about it. (Cue this Chocolate Chip Cookie Peanut Butter Cream Pie…ridiculously long name, ridiculously good pie.)

Pair it with the classic childhood fluffernutter (aka peanut butter + marshmallow) combination and you’ve got C-O-M-F-O-R-T written all over these dessert bars.

I mentioned in this Flaky Buttermilk Biscuit Recipe that specific groceries had been pretty scarce last week, but this week seems to be better. However, if there are any ingredients you don’t have on hand here, I offer some easy substitutions down below. 😊

Okay, who’s ready to get to baking these awesome (yes, totally biased here) fluffernutter chocolate chip cookie bars??

These Marshmallow Peanut Butter Chocolate Chip Cookie Bars combine everything I love about chocolate and peanut butter into one intensely rich, ridiculously gooey, over-the-top dessert bar.

Not to talk these peanut butter chocolate chip cookie bars up too much, similarly to these Strawberry Blondies, this was one of those recipes where I was shocked at how good these were.

I expected these to be pretty good (because Reeses peanut butter cups), but these were shockingly incredible.

Like, I-ate-most-of-the-pan-in-the-span-of-two-days, incredible.

(But really. This may or may not have happened.)

Chocolate Peanut Butter Marshmallow Cookie Bars Ingredients:

peanut butter & butter
brown sugar & granulated sugar
eggs
vanilla extract
baking soda, salt and all purpose flour
Reeses Cups & Chocolate Chips
Marshmallow Fluff (aka Marshmallow Creme)

How Do I Make These Marshmallow Stuffed Peanut Butter Chocolate Chip Cookie Bars?

Peanut butter and butter are mixed together until creamy. Brown sugar and granulated sugar are added into the peanut butter/butter mix.
Next, the eggs and the vanilla extract are added and mixed together.
Baking soda, salt and all purpose flour is added to the batter and mixed until combined.
The chocolate chips and reeses cups are added in last.
Half of the dough is pressed into a baking pan. The marshmallow fluff is dolloped on top. The rest of the cookie dough is pressed on top.
Bake these chocolate peanut butter cookie bars until the top is lightly golden brown.

Peanut Butter Chocolate Chip Cookie Bars stuffed with Marshmallow Fluff Recipe Substitutes:

You can use all natural peanut butter or a peanut butter with sugar in it. I used all natural peanut butter (so if you use a sugary peanut butter, just note that these bars will be even sweeter).
If you do not have peanut butter, you can use all butter in this recipe. With the reeses cups, these cookie bars will still have some peanut butter flavor, just not quite as much.
You can also use a nut butter instead of peanut butter.
You need flour, baking soda and salt. Those 3 ingredients cannot be substituted.
If you do not have reeses cups, you can use all chocolate chips. Or you can use peanut butter chips, if you have those.
Marshmallow fluff makes these chocolate peanut butter cookie bars extra rich and gooey. However, you can use marshmallows instead (spread half the cookie dough in the bottom of a pan, sprinkle a layer of mini marshmallows or large marshmallows cut in half, then top with the rest of the cookie dough). Just note, if you use marshmallows instead of marshmallow fluff, these will not be as gooey.
You can use all brown sugar if you need to, or all granulated sugar if you need to. It is best to use the ratio I have specified in the recipe, but if you do not have access to both of these ingredients, one or the other will work.

Marshmallow Peanut Butter Chocolate Chip Cookie Bars Tips & Tricks:

The base of these bars is a peanut butter chocolate chip cookie recipe. Peanut butter is substituted for half of the butter in my favorite chocolate chip cookie recipe, and Reeses peanut butter cups are also substituted for half of the chocolate chips.
I like to line the pan with nonstick foil because it makes it so easy to remove the cookie bars from the pan. If you don’t have nonstick foil, you can use parchment paper or baking spray.
You can use a 9×9 pan or an 11×7 pan. If you use a 9×9, the bars will be very thick. If you use the 11×7 pan, they will be slightly thinner.
To keep these bars as gooey as possible, bake the cookie bars until the bars have risen and are lightly golden brown. The centers will remain soft, gooey and perfect.
The dough is fairly thick so you will need to press the cookie dough into the baking pan. Make sure that you use only half of the cookie dough for the bottom layer. Then add the marshmallow layer. They top with the remaining cookie dough.