Preheat oven to 350 degrees F. Grease 36 mini muffin cups with cooking spray. Whisk baking soda, baking powder and flour together in a medium bowl. Using a stand mixer, mix butter, peanut butter and sugar for about 2 minutes. Beat in egg, milk and vanilla. Slowly add flour mixture until well blended. Roll into 3/4 inch balls and place a ball into each muffin cup. Using a tart tamper, press into the center of each ball to form a tart. Bake 12 minutes. Remove from oven and immediately press a peanut butter cup into the center of each cookie. Cool completely on wire rack before removing.