• Measure the almond flour and powdered sugar (by weight, please!) and sift them into a bowl. Set aside.
• In the bowl of a stand mixer, combine room temperature egg whites and cream of tartar and whisk until frothy (1-2 minutes). Gradually add in the granulated sugar (1 tablespoon at a time) and mix until stiff peaks form (7-9 minutes). The meringue should stick straight up when you remove the whisk.
• Sift half of the almond flour and powdered sugar into the meringue and fold by going around the bowl and straight through the center of the meringue. Continue folding until there are no dry spots remaining. Sift in the remaining almond and powdered sugar mixture and fold until you get a “lava-like” consistency (about 60 folds, this is not accurate but a good starting point). You should be able to pick up your spatula and draw a figure 8 with the batter without it breaking off. The batter should also disappear back into the bulk after about 15-20 seconds. Be careful not to overmix the batter or you will lose air bubbles from the egg whites.
• Prepare a piping bag with a large round tip. Use a large mug or glass to hold the piping bag while you fill with the macaron batter. Add a silicone mat or parchment paper to a baking sheet. Holding the piping bag straight up, pipe about 1 ½” circles of batter.
• Next, tap the baking sheet 5 times against the counter to remove any air bubbles. Use a toothpick to pop any air bubbles that come to the surface.
• This step is very important. Allow the shells to set for about 20-40 minutes or until a “skin” forms on the outside (it might take longer depending on your environment). You should be able to touch the top of the shells without batter coming off on your finger. The macaron shells are ready to bake, when they are no longer tacky.
• Preheat the oven to 300°F/150°C while the macarons are drying.  Bake for 15-17 minutes or until you can touch the top of the shell and it does not move around on the “feet”. You may need to rotate the pan midway if you know that your oven has cold spots. Otherwise, do not open the oven until 13 minutes have gone by. The macarons are done when they have puffed up and no longer stick to the silicone pan or parchment paper.
• Remove the macaron shells from the oven and allow them to cool COMPLETELY before trying to remove them from the pan.

To Make the Buttercream:

• While the macarons are cooling, prepare the buttercream by adding the butter into the bowl of a stand mixer and cream until nice and smooth.
• Add in powdered sugar one cup at a time and fully incorporate.
• Pour in heavy whipping cream and slowly increase speed to high and whip for 2-3 minutes until you get a whipped consistency.
• Add in the crumbled Christmas tree cakes last and mix on high speed until combined and smooth.
• Add to a piping bag with a large round piping tip, I used Wilton #1A.
• Flip over half of the shells and pipe a small amount of buttercream on each shell and top with the remaining shells.

For the Topping:

• Dip the top of one of the shells into white chocolate and sprinkle with green sprinkles. Repeat with half of the shells.
• Use a small piping tip and pipe red lines of buttercream or royal icing on top of the white chocolate. Use a cake as a reference.
• Place in an airtight container in the refrigerator for at least 24 hours to “mature” this will give you the best results. Bring the macarons to room temperature and serve.