Sift powdered sugar and almond flour together twice, then set aside.

Whip egg whites in a clean bowl until foamy. Gradually add granulated sugar and cream of tartar, beating until stiff peaks form.

Fold in green gel food coloring until desired hue is achieved.

Gently fold the sifted dry ingredients into the egg whites until the batter flows thickly.

Pipe macaron batter onto parchment-lined sheets, shaping into trees or circles.

Bake at 300°F (150°C) for 14 to 16 minutes, rotating halfway through.

Let macarons cool on sheets for 10 minutes before transferring to a wire rack.

Beat softened butter until fluffy, then gradually mix in powdered sugar, vanilla, heavy cream, and salt.

Optionally, fold in crumbled snack cakes.

Pair cooled shells, piping filling onto one and sandwiching with another.

Drizzle with melted white chocolate and sprinkle with decorations. Refrigerate for 24 hours before serving.