These Peanut Butter S’mores Cookie Bars are made with a chewy, graham cracker infused peanut butter cookie base, are loaded with pockets of melty mini marshmallows, and decorated with real milk chocolate bar pieces!
These peanut butter s’mores cookie bars are a rare recipe of mine that turned out absolutely perfectly on the first try.
It almost never happens that I like a recipe enough the very first time I make it that I don’t feel the need to make it again, tweaking this and that trying to improve the flavor or chewiness or whatever I have in my mind at the moment that needs improvement. Despite this, these cookie bars didn’t even make it to my photography studio (AKA my living room) and I ended up having to make them again, anyway, just so that I could take pictures.
I’d mostly like to blame Zach for eating half the pan before they even finished cooling, but since I ate the other half I don’t think that would be entirely fair. They’re undoubtedly addictive, and totally delicious, and I think you’re going to enjoy them just as much as we did.
Self control, what is that, anyway?
Here’s what I love about these peanut butter s’mores cookie bars, and what I think you’re going to love about them, too.
- Subtle graham cracker flavor that complements the peanut butter perfectly 👌🏼
- Soft and chewy cookie base! Not only is the cookie layer already soft on its own, but all those mini marshmallows that you’re going to fold into the batter are going to melt away as they bake creating gooey tunnels of chewy marshmallow goodness (and a lightly crisp, crackly top wherever the marshmallows touch the surface of your cookie bars). It’s absolutely heaven. Yum. I’m so hungry right now.
- Real Hershey bars for that authentic s’mores flavor. Sure, you could use milk chocolate chips but real s’mores flavor calls for real s’mores ingredients, so grab yourself 4 Hershey bars, maybe make it 5 because if you’re anything like me you’re going to eat a whole candy bar’s worth while you’re chopping them up, anyway.
Tips for Making Peanut Butter S’mores Cookie Bars
I swear I didn’t mean to make this post just a bunch of bullet points, but let’s talk tips now.
- Crunchy or creamy peanut butter will work in this recipe, but I don’t recommend using a natural peanut butter.
- This batter is thick, so thick that I actually broke one of my favorite spatulas trying to stir in the marshmallows and chocolate by hand. The milk does help thin it out a bit, just beware that it’s going to take a little muscle if you want to stir the add-ins by hand, and it may be too thick even for an electric hand mixer.
- I recommend using a metal pan when baking simply because that’s what I’ve used and tested. A glass pan will work, but it will likely take your cookie bars longer to finish baking.
- As with most of my cookie bar recipes I always opt for my baked goods to be just slightly under-baked when pulling them out of the oven. I recommend using a toothpick and looking for a few moist crumbs (not wet batter, just fudgy crumbs) on the toothpick rather than waiting for a completely clean one to indicate it’s done. The peanut butter s’mores bars will finish cooking as they cool, and pulling them out before they’re completely baked through helps to keep them soft and chewy.
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Peanut Butter S'mores Bars
- 1 cup unsalted butter softened (227g)
- 1 cup creamy peanut butter I don't recommend using natural peanut butter (235g)
- 1 cup light or dark brown sugar tightly packed (200g)
- 1 cup granulated sugar 200g
- 1 large egg + 1 large egg yolk
- 1 1/2 teaspoons vanilla extract
- 2 3/4 cups all-purpose flour 345g
- 1/2 cup graham cracker crumbs 65g
- 1 teaspoon baking powder
- 1 teaspoon cornstarch
- 1/2 teaspoon salt
- 2 Tablespoons milk
- 4 1.55 oz milk chocolate Hershey bars chopped into pieces*
- 1 ½ cups mini marshmallows 72g
- Preheat oven to 350F (175C) and line a 13x9 metal pan with parchment paper or grease and flour the sides and bottom of the pan.
- Combine butter, peanut butter, and sugar in a large bowl and use an electric mixer to beat until light, creamy and well-combined.
- Add egg/egg yolk and vanilla extract, and stir well.
- In a separate bowl, whisk together flour, graham cracker crumbs, baking powder, cornstarch, and salt.
- Gradually, on low speed, add flour mixture to peanut butter mixture, pausing occasionally to scrape down sides of bowl.
- Add milk and stir until combined.
- Fold in chopped Hershey bars and mini marshmallows -- the batter will be thick (I broke a spatula stirring it so proceed with caution!).
- Spread batter into prepared ban and bake on 350F (175C) for 25-28 minutes (toothpick inserted in center should come back mostly clean with only a few crumbs)
- Allow to cool completely before cutting and serving.