Preheat oven to 375 degrees.
Sift together flour, baking soda and salt; set aside.
Using an electric mixer, cream together butter, peanut butter, 1/2 cup granulated sugar and light brown sugar.
Add egg, milk and vanilla into the butter mixture; beat until well blended.
Gradually add flour mixture, mixing thoroughly.
Spray, oil or line a cookie sheet with nonstick liner and set aside.
Roll dough into 1-inch balls or use a 2-inch scoop for larger cookies.
Roll cookies in sugar and place 2 inches apart on cookie sheet.
Bake until very light brown and puffed, 6 to 8 minutes.
Remove sheet from oven and lightly press a candy kiss into center of each cookie, allowing it to crack slightly.
Return to oven until light golden brown, 2 to 3 minutes.
Remove from oven, cool completely and store in an airtight container.