- With the rack in the middle position, preheat the oven to 350°F (180°C). Line two baking sheets with parchment paper or silicone mats.
- In a bowl, combine the flour, baking powder and salt. Set aside.
- In another bowl, cream the butter, sugar and vanilla with an electric mixer. Add the egg and beat until smooth. At low speed or with a wooden spoon, stir in the dry ingredients.
- Shape the dough into balls using about 2 tbsp (30 ml) of dough for each cookie. Place 10 balls on each prepared baking sheet. With a fork, flatten the dough to create a criss-cross pattern. Sprinkle with coloured sugar crystals, if desired.
- Bake one sheet at a time for 12 to 14 minutes or until the edges are lightly golden brown. Let cool completely.
- The cookies will keep in an airtight container for 1 week at room temperature or 3 months in the freezer.