1. In a bowl, combine flour, baking powder and salt. Set aside.
2. Using an electric mixer, cream butter with sugar, brown sugar and vanilla. Add egg and mix until smooth. With the mixer set on low, or using a wooden spoon, stir in dry ingredients. Shape dough into 2 disks. Wrap in plastic wrap and refrigerate for 1 hour.
3. Place rack in centre of oven. Preheat oven to 180 °C (350 °F). Line two baking sheets with parchment paper.
4. On a lightly floured work surface, roll out one disk of dough at a time to a thickness of 5 mm (¼ in.). Use a cookie cutter to cut out cookies. Arrange cookies on baking sheets. Reroll scraps and reuse.
5. Bake one baking sheet at a time for 10–12 minutes or until cookies are slightly golden. Cool completely.
6. To make the icing, whisk together icing sugar, milk and food colouring until smooth and well combined.
7. Decorate cookies by dipping them in icing or using a pastry bag. Top icing with sprinkles, if desired. Leave to set on a rack for 4 hours.

Chef’s secret

• Don’t like icing? You can also dip part of the cookies in chocolate that has been melted in a double boiler and allow the chocolate to cool until set.