1. Preheat the oven to 350°F (175°C) and line baking sheets with parchment paper.

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

3. Add in the egg and vanilla extract, and mix until combined.

4. In a separate bowl, whisk together the flour, baking powder, and salt.

5. Gradually mix the dry ingredients into the wet mixture until a soft dough forms.

6. Lightly flour a clean surface and roll out the dough to about ¼ inch thickness.

7. Use cookie cutters to cut out desired shapes and place them on the baking sheets.

8. Bake for 9–11 minutes, or until the edges are just barely golden.

9. Remove from the oven and let cool completely on a wire rack.

10. To make the icing, mix powdered sugar with milk until smooth and pipeable.

11. Decorate the cooled cookies with icing and sprinkles.

12. Let the icing set before serving or storing.