Preheat your oven to 350°F (175°C) and grease a mini muffin tin with non-stick spray.

Whisk together ½ cup of melted unsalted butter and 1 cup of granulated sugar until glossy.

Add 2 large eggs and 1 teaspoon of vanilla extract, stirring until smooth and creamy.

Sift in ⅓ cup of unsweetened cocoa powder, ½ cup of all-purpose flour, and ¼ teaspoon of salt.

Gently fold the dry ingredients into the batter until just combined.

In a separate bowl, mix ⅓ cup of creamy peanut butter, 2 tablespoons of powdered sugar, and 1 tablespoon of melted butter.

Fill each muffin tin cup halfway with brownie batter.

Drop a dollop of the peanut butter mixture into the center of each brownie batter base.

Cover each peanut butter dollop with more brownie batter.

Bake for 18-22 minutes, until edges are set and a toothpick comes out with a few moist crumbs.

Let cool for about 10 minutes before transferring to a wire rack.