Begin by sifting the powdered sugar and almond flour together twice to ensure a fine, lump-free texture.

In a clean mixing bowl, beat the room-temperature egg whites on medium speed until foamy. Gradually add the cream of tartar and granulated sugar until stiff peaks form.

Once egg whites are at stiff peaks, gently fold in green gel food coloring until desired color is achieved.

Carefully fold the sifted almond flour and powdered sugar mixture into the egg whites until the batter flows like lava.

Transfer the macaron batter into a piping bag fitted with a round tip and pipe desired shapes onto parchment-lined baking sheets.

Allow piped macarons to rest at room temperature for 30–60 minutes until a skin forms on their surface.

Preheat oven to 300°F (150°C) and bake rested macarons for 14–16 minutes.

To prepare the creamy filling, beat the softened butter until creamy, then mix in powdered sugar, heavy cream, vanilla extract, and salt.

Once shells are cooled, pipe filling onto the flat side of one shell and sandwich with another shell.

Drizzle melted white chocolate over assembled macarons and sprinkle with holiday-themed decorations.