Cream the Butters and Sugars: In a large mixing bowl, combine the butter, granulated sugar, and brown sugar. Cream together for about 4 minutes until light and fluffy.

Mix in the Remaining Wet Ingredients: Add peanut butter, egg, milk, and vanilla extract to the creamed mixture. Mix for an additional 2 minutes.

Combine the Dry Ingredients: In a separate bowl, stir together flour, baking soda, and salt. Gradually add to the wet ingredients until just combined.

Chill the Dough: If time allows, cover and chill dough for 30 minutes.

Preheat the Oven: While the dough chills, preheat oven to 375°F (190°C) and prepare baking sheets.

Form the Cookie Balls: Roll about 1 inch of dough into balls and coat in sugar.

Bake the Cookies: Place on baking sheets and bake for 8-10 minutes until edges are set.

Add Hershey's Kisses: Press a Hershey's Kiss into the center of each cookie immediately after removing from the oven.