– 40 Mini Reese's peanut butter cups, 1" size – 1/2 cup (1 stick) butter, room temperature – 1/2 cup granulated sugar – 1/2 cup light brown sugar – 1/2 cup creamy peanut butter – 1 large egg – 1 1/2 tsp. vanilla extract – 1 1/2 cups all purpose flour – 1 tsp. baking soda – 1/2 tsp. salt