Preheat oven to 375°F and line one or two large baking sheets with parchment paper. Set aside.
Whisk the cookie mix and cocoa powder together in a large mixing bowl.
17.5 ounces peanut butter cookie mix, ¼ cup cocoa powder
Using a hand mixer, beat in the egg and melted butter until the dough is smooth, about 2 minutes.
1 large egg, 5 tablespoons salted butter
Using a 1½-tablespoon cookie portion scoop, make balls of dough and place them 2 inches apart on the prepared baking sheet(s).
Use a fork to gently press a criss-cross pattern into the top of the cookies but don’t squash them totally flat.
Sprinkle each cookie with a little sugar, optional, and then bake for 7-10 minutes, or just until the edges are set.
Granulated sugar
Remove from the oven and allow to cool for 3-5 minutes on the baking sheet before removing to a cooling rack or serving warm.
Notes
You can use your favorite homemade peanut butter cookie recipe instead of boxed mix; simply add cup of cocoa powder and a bit of water until the dough comes together.
You can use any cocoa powder you have on hand for this recipe.
If you want a less chocolatey cookie you can substitute this for ½ cup of chocolate chips instead.
You can use neutral oil, such as vegetable, canola, or coconut oil, in place of the butter.
You can top these cookies with brown sugar instead of granulated sugar.
If you don’t have multiple baking sheets, be sure to cool your baking sheet between batches. You can also cover the cookie dough and refrigerate it between batches to help ensure that the cookies don’t flatten out too much. To help your baking sheet cool faster you can fan it in the air several times or hold it in front of a fan to help cool it.
Be sure to whisk together the cookie mix and cocoa powder well before adding the other ingredients or you may end up with peanut butter cookie mix chunks in your cookies. The cocoa tends to be fine enough it doesn’t clump but the cookie mix may if not well mixed.
Don’t overbake the cookies. If they are overbaked, they will get hard and crispy. The cookies should have a set look to them and the edges should be just firm when you remove them from the oven. They will continue to set as they cool.
These cookies can be eaten warm or cooled. If you want to reheat them you can microwave them for 10 seconds but be sure to include a damp paper towel when doing so to keep the cookies soft!
Nutritional information does not include optional ingredients.
Storage: Store chocolate peanut butter cookies in an airtight container at room temperature for up to 5 days, in the refrigerator for up to 1 week, or in the freezer for up to 1 month.