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 ¾ 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.
Nutrition is for one cookie tart only. The mini peanut butter cup adds an additional 44 calories, .8 g protein, 4.4 carbs and 2.4 g fat.