Sift the powdered sugar and almond flour together in a bowl using a fine-mesh sieve; repeat this process twice to ensure a smooth texture.

In a clean mixing bowl, begin beating your room temperature egg whites until foamy. Gradually add cream of tartar and granulated sugar, a tablespoon at a time until you achieve stiff peaks.

Gently fold in a few drops of green gel food coloring into the whipped egg whites until you achieve a vibrant color.

Gradually fold in the prepared almond flour mixture into the egg whites using a spatula until the batter flows slowly.

Transfer the macaron batter into a piping bag fitted with a round tip. Pipe tree shapes or simple circles on parchment-lined baking sheets.

Preheat your oven to 300°F (150°C). Once the macarons have rested and feel touch-dry, bake for 14-16 minutes, rotating trays halfway.

In a mixing bowl, beat the softened unsalted butter until fluffy. Gradually mix in powdered sugar, vanilla extract, a pinch of salt, and heavy cream until creamy.

To assemble, pipe filling onto the flat side of one macaron shell and sandwich with a second shell.

Melt white chocolate and drizzle over the assembled macarons. Finish with red and green sprinkles or edible gold stars.

Refrigerate assembled macarons for at least 24 hours to enhance flavors before serving.