You can make the dough a few days in advance. Keep it tightly wrapped in the refrigerator and let it stand at room temperature for a half hour before rolling out. Makes about 4 dozen.
1 cup unsalted butter, at room temperature
2 cups confectioner’s sugar, sifted
2 large eggs
1 large egg, separated
1 tsp. vanilla extract
1/2 tsp. almond extract
3-1/3 cups all-purpose flour
1/2 tsp. baking powder
1/4 tsp. salt
1/4 cup granulated sugar
1 tsp. ground cinnamon
Beat the butter and confectioner’s sugar with an electric mixer on medium speed until creamy. Add the eggs, egg yolk, vanilla, and almond extract (reserve the egg white for later). Mix until smooth and fluffy.
In a medium bowl, sift together the flour, baking powder, and salt. Add to the butter mixture and mix at low speed just until incorporated. Shape the dough into a flat disk and wrap it in plastic wrap. Chill in the refrigerator for 2 hours.
Preheat the oven to 350°F. Line cookie sheets with parchment paper. On a lightly floured counter, roll out the dough to a thickness of 1/8 inch. Cut out circles with a 2-1/2-inch biscuit cutter. Place the rounds on the prepared pans and brush with lightly beaten egg white. Stir together the granulated sugar and cinnamon in a small bowl, and sprinkle over the cookies. Gently press five almond slices in a spoke design in the center of each cookie.
Bake for 4 minutes. Remove the pan from the oven and gently press the almonds into the cookies again. Sprinkle with additional cinnamon-sugar if desired. Bake for 10 more minutes or until the middles resist your touch when lightly pressed. Remove the cookies to wire racks and let cool completely.