In a mixing bowl, beat together ½ cup of creamy peanut butter, ¼ cup softened butter, and ½ cup brown sugar until light and fluffy, about 2-3 minutes. Add 1 egg and 1 teaspoon of vanilla extract, mixing until well combined.

In a separate bowl, whisk 1 cup of all-purpose flour, ½ teaspoon of baking soda, and ¼ teaspoon of salt, then gradually incorporate this dry mixture into the peanut butter mixture until just combined.

In a clean bowl, mix ¼ cup melted butter with 1 cup white sugar until smooth and creamy, ensuring there are no lumps.

Stir in ⅓ cup cocoa powder, 1 egg, and 1 teaspoon of vanilla extract, blending well.

Gently fold in ½ cup all-purpose flour, ¼ teaspoon baking powder, and ¼ teaspoon of salt, followed by adding ½ cup chocolate chips until fully combined.

Cover both the peanut butter dough and brownie dough with plastic wrap and refrigerate them for about 30 minutes.

Preheat your oven to 350°F (175°C) while you prepare a parchment-lined baking sheet.

Using a cookie scoop, place 1-2 tablespoon portions of the peanut butter dough and brownie dough side by side on the sheet. With a toothpick, gently swirl the two doughs together for that beautiful marbled effect.

Slide the baking sheet into the preheated oven and bake the cookies for 9-11 minutes.

Once baked, let the cookies rest on the baking sheet for 5-10 minutes, then carefully transfer them to a wire rack to cool completely.