2 cups flour, plus extra for dusting
1/2 teaspoon baking powder
1/4 teaspoon kosher salt
1 large egg, at room temperature
2 tablespoons milk
1 teaspoon vanilla extract
1 stick unsalted butter, at room temperature
1 cup sugar
3 egg whites
1 pound confectioners’ sugar
1 teaspoon lemon juice
Food coloring, optional
1. In a medium bowl, combine flour, baking powder, and salt. Set aside.
2. In a small bowl, combine egg, milk, and vanilla.
3. In an electric mixer fitted with paddle attachment, cream together butter and sugar until light and fluffy. Add egg mixture and mix until combined. Slowly add flour, a little at a time until incorporated. Wrap dough in plastic wrap, flatten into a disk, and refrigerate for about 30 minutes.
4. Preheat oven to 350°F. Line a baking sheet with parchment paper and set aside.
5. On a lightly floured surface, roll dough until about 1/4-inch thick. Cut out with lightly floured cookie cutters and place cookies on prepared baking sheet. Bake for 8-10 minutes, until just lightly browned. Transfer cookies to a cooling rack and allow to cool completely.
6. Make icing. Using an electric mixer, whisk egg whites, sugar, and lemon juice until light and fluffy, about 5 minutes (icing should be glossy when ready).
7. If adding food coloring, either add a few drops into mixture and stir until combined, or divide icing into separate bowls for multiple colors.
Makes approximately 18 cookies.