Preheat your oven to 350°F (175°C).

In a large mixing bowl, combine softened butter and creamy peanut butter along with granulated sugar and brown sugar. Beat until light and fluffy, about 2-3 minutes.

Add in one large egg and a splash of vanilla extract, mixing until well-blended.

In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually add this to the wet ingredients, stirring gently until just combined.

Roll small portions of dough into 1-inch balls and place in greased mini muffin pans.

Bake for 8-10 minutes until lightly golden around the edges but still soft in the center.

Press a mini Reese’s Peanut Butter Cup into the center of each cookie immediately after baking.

Allow cookies to cool in the pan for about 5 minutes before transferring to a wire rack to cool completely.