Cream butter well, gradually adding sugar and beating until smooth. Add egg yolk and flavoring. Add flour gradually, and if using almonds, add now. Roll into desired shapes and bake at 325 degrees F approximately 20 minutes. DO NOT BROWN.
While cookies are baking, sift powdered sugar on a sheet of wax paper large enough to hold cookies when taken out of the oven. Remove cookies from oven just as they begin to turn color at the bottom (tops should still have no color). Immediately place cookies onto sifted powdered sugar, at least 1/4-inch apart. Immediately sift powdered sugar to completely cover cookies.
Traditional shapes for kourambiedes (Greek Christmas Cookies) are crescents or diamond shapes. After cookies have cooled, you may want to place them in individual paper cups. They can be stored in an airtight container for several weeks.