In a bowl, whisk the flour, baking powder and salt.
in the bowl of a standing mixer, cream together the butter and sugar until light and fluffy, about 3 minutes.
Add the egg and vanilla and mix until incorporated.
Gradually add the flour mixture until the dough comes together.
Place the dough on a piece of parchment paper, shape into a disk, cover and refrigerate until firm, about 20-30 minutes.
Preheat oven to 325F.
Roll out dough to 1/4 inch thick.
Use cookie cutters to cut out desired shapes. Place on a Silpat or parchment lined baking sheet
Bake for 10-12 minutes, until the edges begin to turn golden.
Allow the cookies to cool completely before decorating.
For the icing: combine the ingredients in a bowl and stir until smooth.
(to make dye-free red or blue icing substitute the juice from frozen raspberries, blueberries or blackberries for milk).