Preheat oven to 375 degrees. Combine softened butter, cooked egg yolks, sugar and almond extract, and mix with an electric hand mixer. Add flour slowly to incorporate into batter until batter is smooth. Drop cookies on a parchment-lined cookie sheet by full teaspoonfuls. Flatten each slightly with fork tongs. Using a pastry brush, place some of the egg white on each cookie top and sprinkle as desired. Bake for 10 to 12 minutes, just until bottoms are lightly browned. Makes about 2 dozen, and recipe is easily doubled.