• 1. Sift flour with baking powder, soda, salt, and nutmeg; set aside.
• 2. In large bowl of electric mixer, at medium speed, beat butter, sugar, and egg until light and fluffy.
• 3. At low speed, beat in sour cream and vanilla until smooth.
• 4. Gradually add flour mixture, beating until well combined.
• 5. With rubber scraper, form dough into a ball. Wrap in waxed paper or foil; refrigerate several hours or over night.
• 6. Divide dough into 4 parts. Refrigerate until ready to roll out.
• 7. Meanwhile, preheat oven to 375 degrees. Lightly grease cookie sheets.
• 8. On well-floured surface, roll dough, one part at a time, 1/4 inch thick.
• 9. With floured star shaped cookie cutters, cut out cookies (minimum 3 to 4 of each size). Using spatula, carefully place cookies 2 inches apart on cookie sheet. If desired, re-roll trimmings and cut.
• 10. Bake 10 to 12 minutes, or until golden. Remove to wire rack; cool.

To Create the Christmas Tree Cookie Stack:

• Using a total of 18 cookies, I made my Christmas tree rather tall, but you can use fewer cookies and make it smaller if you like. I used 3 or 4 of each size of the six star shaped cookies.
• Begin by selecting one of the largest cookies for the base. Using the royal icing as glue, stack another cookie of the same size or larger on top of the base cookie. You'll rotate each cookie slightly, so that the points are exposed. Repeat this process until your tree is complete, using smaller cookies as you work your way up. Place and glue one of the smallest stars in an upright position, at the top of the tree.
• Once your tree is built, using a leaf tip, add royal icing snow to the tip of each star. Sprinkle royal icing with white sparkling sugar sprinkles. Do this as you work your way up. If you wait, the icing will harden and the sugar sprinkles will not stick.