Preheat oven to 375 degrees F. Mix together the flour, salt and baking soda. Set aside.
Cream together the butter, sugar, peanut butter and brown sugar until fluffy. Beat in the egg, vanilla and milk. Add the flour mixture; mix well. Shape into balls and place each into a mini muffin pan.
Bake at 375 degrees for about 8 minutes. Remove from oven and immediately press a mini peanut butter cup into each ball. Cool and carefully remove from the pan.
Recipe by Sports Mom Survival Guide at https://www.sportsmomsurvivalguide.com/peanut-butter-cup-cookies/