This is a classic French cookie originating in Normandy France. These cookies are delicious plain, but they can also be flavored with ground nuts or zests and they can even be sandwiched together with jam or preserves, ganache, or lemon curd.
In the bowl of your electric mixer (or with a hand mixer), beat butter and sugar until light and fluffy (2-3 minutes).
Add the egg and vanilla extract and beat until blended.
In a separate bowl, whisk together the flour, baking powder and salt.
Add the flour mixture to the butter mixture and beat just until incorporated. Do not over mix the dough.
Transfer the dough to a lightly floured work surface, knead the dough a few times to bring it together, and then divide the dough in half.
Wrap each half in plastic wrap and refrigerate until firm (at least an hour).
Preheat oven to 350 degrees F (177 degrees C) and place rack in the center of the oven.
Line two baking sheets with parchment paper and set aside.
Remove one portion of the dough from the refrigerator and place on a lightly floured work surface. Roll out the dough until it is 1/4 inch (1 cm) thick. Using a lightly floured 2 inch (5 cm) round fluted cookie cutter, cut out the cookies, placing them on the prepared sheet.
Place the baking sheet of cut out cookies in the refrigerator for about 15 -20 minutes to chill the dough.
Meanwhile, in a small bowl, whisk the egg with the water for the egg wash. Remove the cookies from the refrigerator and brush the tops with the egg wash.
Then, with the tines of a fork (or I like to use the end of a toothpick), make a crisscross pattern on the top of each cookie.
Bake cookies in the preheated oven for about 12-14 minutes (depending on size of cookie) or until golden brown around the edges.