Using a stand mixer or handheld mixer, beat together the butter and sugar until well-combined. Add the egg, milk, and vanilla extract and beat to combine. Don't beat this mixture too much, as you don't want to aerate the dough.

Sift together the flour, baking powder, and salt and add to the wet ingredients. Stir just until combined.

Form dough into a ball. Wrap in plastic and refrigerate for at least 2 hours and up to 72.

When ready to bake, preheat oven to 350°F.

Divide dough into four pieces. Sprinkle your board with flour and roll the dough out to 1/4 inch thickness. Cut with your favorite cutters and place on a parchment lined cookie sheet. Bake for 6 to 8 minutes, until cookies are set but not too browned.

Let cookies cool on sheet for 1 minute, then carefully transfer to a cooling rack. Repeat with remaining dough.