Sift the powdered sugar and almond flour together in a bowl, ensuring to sift twice. Set aside.

Whip the egg whites until foamy. Gradually add cream of tartar and granulated sugar, whipping until stiff peaks form, about 5-7 minutes.

Fold in green gel food coloring and almond flour mixture in three parts until the batter flows smoothly.

Pipe tree shapes or circles on a lined baking sheet and tap to release air bubbles.

Rest the piped macarons at room temperature for 30-60 minutes until they feel dry.

Preheat oven to 300°F (150°C) and bake macarons for 14-16 minutes, rotating trays halfway.

Beat softened butter until fluffy, then mix in powdered sugar, vanilla, heavy cream, and salt. Fold in crumbled chocolate snack cakes.

Pipe filling onto half of the shells and sandwich with the remaining shells. Optionally drizzle with white chocolate.

Refrigerate assembled macarons for at least 24 hours before serving for improved texture.