Cream together butter, sugars, egg, peanut butter, vanilla and milk.
Mix together flour, salt and baking soda. Blend with creamed mixture.
Shape by rounded teaspoons into balls and roll in sugar.
Place on ungreased cookie sheet and bake at 375 degrees F. for 8 minutes.
Remove from oven and place a candy kiss in the middle of each cookie, pressing down so that the cookie cracks around the edge.
Return to oven and bake 2 minutes longer.