Make the Macaron Shells:

1. Prepare Ingredients:
   Sift together the powdered sugar and almond flour into a large bowl. Discard any large pieces.
2. Whip the Egg Whites:
   In a clean, dry bowl, beat the egg whites on medium speed until frothy. Gradually add the granulated sugar and continue beating until stiff, glossy peaks form. Add vanilla extract and a few drops of red gel food coloring, mixing until evenly colored.
3. Fold the Batter:
   Gently fold the dry ingredients into the meringue using a spatula. Mix until the batter flows like lava and forms ribbons that hold their shape for about 10 seconds before blending back in.
4. Pipe the Macarons:
   Transfer the batter to a piping bag fitted with a round tip. Pipe 1.5-inch circles onto a silicone baking mat or parchment-lined baking sheet. For Santa hats, pipe small red triangles at the top of some shells.
5. Rest the Macarons:
   Tap the baking sheets firmly on the counter to release air bubbles. Let the macarons sit at room temperature for 30–60 minutes, or until the tops form a skin and no longer stick to your finger when touched.
6. Bake:
   Preheat the oven to 300°F (150°C). Bake the macarons for 14–16 minutes, one tray at a time, rotating halfway through. Allow the shells to cool completely before removing them from the baking sheet.

Make the Filling:

1. In a bowl, beat the butter until creamy. Gradually add powdered sugar, heavy cream, and vanilla extract, beating until light and fluffy.

Assemble the Macarons:

1. Pair the macaron shells by size. Pipe or spread the filling onto the flat side of one shell and sandwich it with another.

Decorate:

1. Use white royal icing or melted white chocolate to create Santa’s beard and hat trim.
2. Add eyes using an edible marker or melted dark chocolate.
3. Tint a bit of royal icing or buttercream with pink food coloring for rosy cheeks. Add mini marshmallows or white sprinkles for hat fluff.