Preheat the oven to 350 degrees
Using a mixer, blend together the butter and peanut butter for 30 seconds
Add both sugars and mix for another 30 seconds
Add the egg, milk and vanilla and blend for another 30 seconds
In two batches add the flour, baking soda and salt. Using a spatula, mix until just blended through
Ideally you should chill the dough for at least two hours
Roll each cookie (approx 1 teaspoon of batter) in your palm and then place in a bowl of colored sugar. Carefully roll it around until coated and transfer to a parchment paper lined cookie sheet. If you happen to be using polish pottery, skip the parchment. No need to use non stick spray either
Cook for 5 minutes
Remove from the oven and add a chocolate chip to the center of each cookie immediately