Instructions

To Make The Base Mix

1. Pulse the pistachios a few times until they are roughly ground. Add the granulated sugar and confectioner's sugar. Process until you have a finely ground flour, scraping down the sides of the bowl as needed. Don't over process or you'll make a paste.
2. Move the mixture to a sieve and sift with the cinnamon If you end up with a lot of large bits left, process them again and sift again. Continue grinding and sifting until you have less than a tablespoon of unground nuts. Whisk the ingredients after sifting to be sure they are well combined
3. Divide the base, setting aside 12 oz (336g) for the macaron shells and the remaining for the buttercream filling.

To Make the Macaron Shells

1. Preheat the oven to 325°F. Use a biscuit cutter or glass to draw twenty-four 2" circles on a 1/2 sheet of parchment paper. Line 2 baking sheets with parchment paper and put the paper with the circles underneath the parchment on one of the pans.
2. Whip the egg whites to soft peak. With the mixer running add the 1.5 oz of confectioner's sugar and the salt and whip to full peak. Add the food coloring, 1 drop at a time, until you have a color that you like. Gently fold the pistachio mixture into the whites in two batches. Continue folding until it becomes soft and shiny, but not thin and runny. When you lift the batter with the spatula and let it drizzle back into the bowl it should leave a trail on the surface that slowly fades.
3. Scoop the batter into a pastry bag fitted with a round tip (or cut the tip of a disposable bag). Pipe discs of batter until until they're 1/4" from the edges of the circles you've drawn. Set the pan aside to allow the cookies to dry for about 30 minutes.
4. Touch the top of a cookie to make sure it's dry to the touch, it can be a bit tacky but shouldn't stick to your finger
5. Bake for 7-8 minutes. For even baking turn the trays so the back side is at the front and rotate the trays between racks. Bake for another 5-6 minutes until the shells are dry and the centers are still soft.
6. To check if the shells are baked I like to gently shimmy the top of the shell. If it jiggles separately from the "foot" the inside is still too soft. If it feels soft but is attached to the foot it's done. Be careful handling the shells, it's easy to crack the surface

To Make the Buttercream Filling

1. Combine the softened butter with the remaining base mix, vanilla, rum and optional green color. Whip on medium-high speed until the buttercream lightens in color and becomes aerated.
2. Scoop the buttercream into a clean pastry bag fitted with a small plain tip or cut the tip of a disposable bag
3. Pair up the cooled shells by size. Flip over half the shells and pipe a dollop of buttercream. Sandwich the cookies gently, handling the cookies by the edges and not the tops.
4. The finished cookies should be refrigerated in a covered container for 1 day before serving. The cookies can also be frozen for several weeks. Bring them back to room temperature before serving.