Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a large mixing bowl, combine melted butter, granulated sugar, and brown sugar. Mix well until smooth.

Add the eggs one at a time, mixing thoroughly after each addition, followed by the vanilla extract.

In another bowl, whisk together the flour, cocoa powder, baking powder, and salt until well mixed.

Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Do not overmix.

In a separate bowl, mix the creamy peanut butter with powdered sugar until smooth and fully combined.

Using a cookie scoop or tablespoon, take a portion of the brownie mixture and flatten it in your hand.

Place a small spoonful of the peanut butter filling in the center and bring the edges of the brownie dough over the peanut butter to encase it completely.

Roll it into a ball and place it on the prepared baking sheet. Repeat until all dough is used.

Bake in the preheated oven for about 10-12 minutes until the edges are set.

Do not overbake; the cookies will firm up as they cool.

Allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.