In a medium bowl, whisk together flour, baking powder, and salt.

In a large bowl, cream together softened butter and granulated sugar until light and fluffy.

Beat in the egg, milk, and vanilla extract until well combined.

Gradually add the dry flour mixture to the wet ingredients, mixing until a dough forms.

Divide dough into two disks, wrap in plastic, and refrigerate for at least 1 hour.

Preheat oven to 375°F (190°C) and line baking sheets with parchment paper.

On a lightly floured surface, roll out dough to 1/4-inch thickness.

Cut into desired holiday shapes using cookie cutters and place on prepared baking sheets.

Bake for 10 to 12 minutes or until edges are barely golden.

Allow cookies to cool completely on a wire rack before decorating with royal icing and sprinkles.