Line a sheet tray with parchment paper, set aside. In a medium-sized bowl, stir together the flour, baking soda, baking powder, and salt, set aside.
In a large bowl cream together the butter and sugar until smooth with an electric hand mixer.
Add the egg and mix it in until combined.
Add the milk and vanilla, stir it in until combined, scrape down the sides as needed.
Add in the dry ingredients and mix until combined.
Using a 1.5 tablespoon cookie scoop, scoop out the cookie dough onto the parchment-lined sheet tray. They can be close but not touching. Cover with plastic wrap and chill for at least 2 hours, but best if you can chill overnight.
Preheat the oven to 375°F. Line sheet trays with parchment paper. Pour the decorator’s sugar into a small bowl.
Roll the cookie dough balls between your hands to form a smooth ball. Dip the tops of the dough balls into the decorator’s sugar.
Place them, sugar side up, onto the parchment-lined sheet trays about 2 inches apart.
Bake for 8-11 minutes until lightly golden brown around the edges. Let the cookies cool on the tray for 10 minutes, transfer to a wire rack to cool completely.