In a large mixing bowl, beat together ½ cup of creamy peanut butter, ¼ cup of softened and melted butter, and ¾ cup of brown sugar until light and fluffy, about 2-3 minutes. Mix in one large egg and 1 teaspoon of vanilla extract until well combined.

In another bowl, whisk together ¼ cup of melted butter and ½ cup of white sugar until smooth. Add in ¼ cup of cocoa powder, mixing until fully incorporated, then add another egg and 1 teaspoon of vanilla extract, stirring until silky. Gradually fold in ½ cup of all-purpose flour, ½ teaspoon of baking powder, ¼ teaspoon of salt, and ½ cup of chocolate chips until no dry streaks remain.

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

Scoop 1-2 tablespoons of each dough onto a parchment-lined baking sheet, place them side by side, and gently swirl together with a toothpick, creating a marbled effect.

Preheat your oven to 350°F (175°C) and bake the cookies for about 9-11 minutes until the tops are crackly and the edges are set.

Remove from the oven and let cool on the baking sheet for 5-10 minutes before transferring to a wire rack to cool completely.