In a medium bowl, combine the flour and baking powder. Mix until combined and set aside.
In the bowl of a stand mixer fitted with the beater attachment, combine the butter and sugar. Beat until light and fluffy. Add in the milk, egg, and vanilla extract. Beat until combined.
Slowly add in the flour mixture until a crumbly mixture forms. The dough should come together when pressed with your fingers. Turn the dough out onto a floured work-surface and knead with your hands until a smooth dough ball forms.
Using a rolling pin, roll out the dough to a ½-inch thick. Cut out shapes and place them on a parchment paper (or silpat) lined baking sheet. Now, you can optionally place the cookies in the freezer for 5 minutes before baking to help prevent them from spreading, or you can just pop them in the oven. Either way, bake for 10-12 minutes.
Transfer to a cooling rack and let cool for 10-20 minutes before decorating.