With rack in top third position, preheat oven 375 F. Sift flour, soda and salt onto a piece of waxed paper. In lg bowl, with mixer on high beat butter and peanut butter together until creamy Gradually add 1/2c sugar and all the brown sugar. Beat until li ght in color and consistency Beat in egg, milk, and vanilla. Using wooden spoon, stir in flour. Place remaining granulated sugar in sm bowl. Using 1T of dough for each, form dough into balls. roll in sugar. Place 1 1/2" apart on ungreased baking sheets. Bake one sheet at a time, until edges are set, 8 mins. Remove. Place a kiss in the center of each cookie. Return to oven; continue baking until lightly browned, 2 mins. longer. Cool on sheet 5 mins then transfer to wire racks to cool. Repeat.