Preheat the oven to 375°F. Grease mini muffin pans.
In a small bowl, combine flour, salt, and baking soda. Set aside.
In a large bowl, cream together butter, sugars, and peanut butter until smooth.
Beat in the egg, vanilla, and milk. Mix well.
Gradually add the dry ingredients to the wet ingredients, mixing until combined.
Roll dough into 1-inch balls and place each into a greased mini muffin cup.
Bake for 8 minutes, until lightly golden. Remove from oven and immediately press a Reese’s cup into each cookie.
Cool in the pan for about 10 minutes before transferring to a wire rack to cool completely.