Sift powdered sugar and almond flour together twice to remove lumps and add air.

Beat egg whites until foamy, then add cream of tartar and continue. Beat in granulated sugar slowly until meringue is glossy and holds stiff peaks.

Mix in green gel food coloring until you get a rich, even color.

Gently fold the almond mixture into the meringue until the batter flows like lava and forms a slow ribbon.

Transfer batter to a piping bag fitted with a round tip. Pipe tree shapes or circles onto lined baking sheets, leaving space between each.

Tap the trays firmly on the counter to release any air bubbles, then use a toothpick to pop persistent bubbles.

Rest the piped shells for 30 to 60 minutes until a smooth skin forms on top.

Preheat the oven to 300°F (150°C). Bake one tray at a time on the middle rack for 14 to 16 minutes.

Rotate the tray halfway through baking for even color. Cool completely on the baking mats before removing.

Beat the softened butter until light and fluffy, about 3 minutes on medium speed. Gradually add powdered sugar and beat until smooth.

Stir in vanilla extract, heavy cream, and a pinch of salt. Fold in the crumbled Christmas Tree Cakes gently.

Pair shells of similar size and shape. Pipe a generous dollop of filling onto the flat side of one shell and sandwich with its match.

Drizzle melted white chocolate across the shaped tops and add red and green sprinkles while the chocolate is still soft.

Refrigerate the assembled macarons in an airtight container for 24 hours before serving.