Place the butter, peanut butter, 1/2 cup of the granulated sugar and the brown sugar in the bowl of a mixer. Beat until light and fluffy.

Add the egg, milk and vanilla extract. Beat until thoroughly combined.

Add the flour, baking soda and salt. Beat on low speed until just combined.

Cover the bowl of dough and place it in the freezer for 20 minutes to chill.

Line 2 sheet pans with parchment paper or nonstick baking mats.

Roll the dough into 1 inch balls. Roll each ball into the remaining 1/2 cup of granulated sugar.

Place each ball 1 1/2 inches apart on the prepared pans. Preheat the oven to 375 degrees F.

Chill the pans of cookie dough in the fridge or freezer for 10 minutes before baking.

Bake the pans, one at a time, for 8-10 minutes or until cookies are lightly browned on the edges.

Remove the pans from the oven. Quickly and firmly press a kiss into the center of each cookie.

Let the cookies cool completely, then serve, or store in an airtight container for up to 5 days.