Sift together almond flour and powdered sugar into a mixing bowl.

Make meringue by whipping egg whites with cream of tartar and granulated sugar until stiff peaks form.

Fold the dry ingredients into the whipped meringue until the batter flows like thick lava.

Pipe 1½-inch rounds onto baking sheets and let them rest until dry to the touch.

Bake in a preheated oven at 300°F for 15-17 minutes.

Prepare filling by beating unsalted butter and powdered sugar, then adding heavy whipping cream and crumbled Christmas Tree Cakes.

Assemble by pairing shells, piping filling onto half, and sandwiching with remaining shells.

Decorate by dipping in melted white chocolate and adding sprinkles and icing.

Chill macaron sandwiches for at least 24 hours before serving.