Easy and unfussy, this peanut butter chocolate sheet cake is comfort food in a casserole dish. Sheet cakes are great for a crowd, or dessert for a few days!
We don’t bake nearly enough sheet cakes, darlings. A sheet cake, like this peanut butter chocolate sheet cake, can be overlooked when we bake for the ‘gram. Or whatever your preferred social media. But sheet cakes are comforting, one of those relics of childhood that give you all the warm fuzzies coming out of the oven. It feels “home-y” to cut into a sheet cake, like wearing your favorite cardigan. I baked a sheet cake for friends a few weeks ago, and remembered to dust off this recipe.
This chocolate sheet cake recipe is a sour cream chocolate sheet cake. I like the flavor the sour cream adds to the cake, and the moisture. You won’t actually taste any sour cream, so don’t worry about that, but it does keep the sweetness in check. Balance is a good thing when the urge to pile on all the creamy peanut butter frosting strikes! Of course we give in, and top with the cutest little mini peanut butter cups, because we can. Mini peanut butter cups on top of fluffy peanut butter ice cream over a moist chocolate sheet cake is just right.
Bake this sheet cake in a 9×13″ glass casserole dish. I tried a smaller, cuter one, but the cake overflowed and I had no room for frosting. I also had to clean my oven. To me, sheet cakes should fit rather neatly in their dishes, with room for frosting, so you can cover the dish neatly for storage. Ideally with a lid, but to preserve our beautiful swaths of frosting, probably with plastic wrap. I didn’t want to crust the frosting at the corners. And no one should have to clean burnt chocolate cake out of the oven.
I found the mini peanut butter cups in the candy section of the grocery store. I’ve seen them in the baking section sometimes, so if you want to use them, check both places. If you don’t find them, don’t fret. Sub a mix of chocolate chips and peanut butter chips, or skip topping altogether, it’s just decoration on an already delicious cake. Enjoy, darlings!
- 1 cup milk (room temperature)
- 1 cup sour cream (room temperature)
- 2 large eggs
- 2 cups unbleached all-purpose flour
- 1 3/4 cups granulated sugar
- 1 cup unsweetened cocoa powder
- 2 teaspoons instant espresso powder (optional)
- 2 teaspoons vanilla extract
- 1 teaspoon baking soda
- 1 teaspoon salt
- 1/4 teaspoon baking powder
Peanut Butter Frosting
- 8 tablespoons butter (softened)
- 1/2 cup smooth peanut butter
- 2 cups powdered sugar
- 1 cup mini chocolate peanut butter cups, halved (optional)
- Preheat your oven to 350 F and grease a 9x13" casserole dish.
- In a large mixing bowl, whisk together the milk, sour cream, and eggs.
- Sift together the dry ingredients in a separate bowl, then add dry to wet. Mix just until combined.
- Pour the cake batter into your prepared pan and bake for 30-35 minutes until a toothpick inserted in the center of the cake comes out clean, or with no more than 1-2 moist crumbs attached.
- Allow the cake to cool on a wire rack. When the cake is cool, make the frosting.
- In a large mixing bowl, or stand mixer, whip together the softened butter and peanut butter.
- Add the powdered sugar 1 cup at a time. Scrape the sides of the bowl after each addition.
- Spread the peanut butter frosting over your cooled chocolate cake, and top with mini chocolate peanut butter cups if desired. Enjoy!
Bake the Cake
Make the Frosting
The cake will keep 2 days covered at room temperature, refrigerate for longer storage. Just keep in mind that the refrigerator is very drying to baked goods, so you'll want to consume the cake within a few days.
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