1. Line two baking sheets with parchment paper or silicone mats and prepare a piping bag with a round tip.

2. Sift the almond flour and powdered sugar together into a large bowl, then set aside.

3. In a clean mixing bowl, beat the egg whites until foamy, add the cream of tartar, then slowly add the granulated sugar while whipping to stiff glossy peaks.

4. Mix in the vanilla extract and a small amount of white gel food coloring if you want a brighter white shell.

5. Fold the almond flour mixture into the meringue in batches until the batter flows in slow ribbons and settles back into itself.

6. Transfer the batter to the piping bag and pipe small even rounds onto the prepared baking sheets.

7. Tap the trays firmly on the counter several times and pop any visible air bubbles with a toothpick.

8. Let the shells rest at room temperature until the tops feel dry to the touch.

9. Bake until the shells are set and have developed feet, then cool completely before removing them from the tray.

10. Beat the butter for the filling until creamy, then mix in the powdered sugar, vanilla extract, heavy cream, and melted white chocolate if using.

11. Match the shells by size and pipe filling onto half of them, then sandwich with the remaining shells.

12. Decorate the tops with royal icing or melted white chocolate in snowflake designs and finish with edible glitter if desired.

13. Refrigerate the filled macarons for 24 hours before serving for the best texture.