In a large mixing bowl, beat together 1 cup of creamy peanut butter and 1/2 cup of softened melted butter until fluffy, about 2-3 minutes.

Gradually add 3/4 cup of brown sugar, incorporating an egg and a splash of vanilla extract until blended.

In a separate bowl, whisk together 1 1/2 cups of all-purpose flour, 1/2 teaspoon of baking soda, and a pinch of salt; gently fold this dry mixture into the wet ingredients until just combined.

For the brownie dough, melt 1/2 cup of butter and whisk it with 1 cup of white sugar and 1/3 cup of cocoa powder until smooth.

Mix in another egg and a teaspoon of vanilla extract, ensuring it's well incorporated.

Gradually add 1/2 cup of all-purpose flour, 1/4 teaspoon of baking powder, and a pinch of salt, gently folding in 1/2 cup of chocolate chips until no dry ingredients remain.

Cover both doughs with plastic wrap and refrigerate for 30 minutes.

Preheat the oven to 350°F (175°C). On a lined baking sheet, use a cookie scoop to place 1-2 tablespoons of each dough side by side.

Gently swirl the doughs together to create a marbled effect.

Bake for 9-11 minutes or until the tops are crackly and edges are set.

Let cool on the baking sheet for 5-10 minutes before transferring to a wire rack.