- In a bowl, combine the flour, baking powder, and salt. Set aside.
- In another bowl, beat the eggs with the sugar and vanilla until light and fluffy. Stir in the butter and dry ingredients until the batter is smooth. Shape into a disc with your hands and cover with plastic wrap. Refrigerate for at least 1 hour.
- With the rack in the middle position, preheat the oven to 190 °C (375 °F). Line two baking sheets with parchment paper.
- In a bowl, combine the egg yolk and milk. Set aside.
- On a floured work surface, roll out the dough to about ½-cm (¼-inch) thick. With a 7.5-cm (3-inch) fluted cookie cutter, cut about 20 cookies, reusing scraps. Brush with the egg wash. If desired, sprinkle with coarse sugar crystals.
- Bake for about 13 minutes or until the cookies are golden brown. Let cool.