1. Heat oven to 350 degrees F. Roll out dough and use an assortment of star cutters to cut various stars. For hollow stars, cut out the centers from some large stars using small cutters. Place the stars on baking sheets and bake until just golden, about 12 minutes for large stars, 10 minutes for small stars. Cool completely.
2. Color 1/2 cup Royal Icing each green, light green and chartreuse. Place in pastry bags with tips. Fill another pastry bag with 1/2 cup white icing. Ice stars and decorate with crystal sugar as desired. Allow decorated cookies to set completely, about 3 hours.
3. Assemble the tree on a large serving platter; layer the stars into a triangle. Serve any extra stars alongside. Makes 1 tree, about 36 cookies.
1. Combine flour, baking powder and salt in a bowl; set aside. In mixer bowl, beat butter and sugar until fluffy, 3 minutes. Beat in yolks and vanilla. Add flour mixture and combine. Wrap dough in plastic wrap, chill 1 hour.
2. Roll dough to 3/8 inch thick on a floured surface. Cut as desired. (Dough scraps can be re-rolled up to 2 times.) Bake at 350 degrees for 10 to 12 minutes. Cookies can be stored airtight for up to 5 days. Makes 36 two-inch cookies.
1. Mix together sugar, meringue powder and 1/3 cup water on low speed to soft peaks, scraping down sides of bowl, about 10 minutes. (If not using immediately, store airtight at room temperature up to 3 days; stir before using.)
2. Divide into bowls and color icing as desired. Transfer immediately into piping bags. Makes 2-1/2 cups.