Whisk together the flour, baking soda and salt. Set aside.
In the bowl of a KitchenAid mixer, or regular mixer, beat the butter on medium speed for 5 minutes. Scrape down the sides.
Add the sugar and continue beating for an addiitonal 5 minutes or until fluffy.
Add the egg and vanilla extract, beating until evenly combined.
Then add the flour mixture and beat until mixed.
Finally add the milk to the dough slowly as the mixer runs, adding just enough to soften the dough.
Using a small (1 tablespoon) cookie scoop, portion the cookie dough and shape into balls.
Roll each ball in the red colored sugar.
Place on parchment lined baking sheets about 1 inch apart.
Chill the cookie balls for about 30 minutes.
Bake for 8 to 10 minutes or until the cookies are puffed and the edges are set.
Cool the cookies on the baking sheet for 4 minutes before pressing one candy kiss into the center of each cookie.
Transfer to a wire rack and allow the cookies to cool completely.
The candies will look like they are melting but do not disturb them and they will resolidify into the correct shape.
Notes
Don't add the kisses into the hot cookies immediately after removing them from the oven. Wait a few minutes. If you do, the candies will melt and not hold their shape.