Make the macaron shells:

1. Prepare a baking sheet with a silicone baking mat (or if you have enough, prepare 2 baking sheets).
2. Using a fine mesh sieve over a large mixing bowl on a scale, sift almond flour until you reach 140 grams. Discard any large pieces of almond flour. Repeat with the confectioners’ sugar. Whisk together the almond flour and confectioners’ sugar until very well-combined. Set aside.
3. Add egg whites to the bowl of your stand mixer. Using a whip attachment, beat the mixture, starting on low. Once soft peaks have been formed (about 2 minutes), add the sugar and increase the speed to medium. Once medium peaks are achieved, increase the speed to high. Beat on high until stiff peaks have formed, about 2 minutes.
4. Add in the green food coloring and the pistachio extract and beat until just combined.
5. Remove the bowl from the stand mixer, and place a sieve over top. Pour the dry mixture into the sieve, then sift the dry ingredients into the meringue.
6. Use a rubber spatula to fold the dry ingredients into the meringue. Be careful not to overmix and over-deflate the meringue. The mixture is ready to be piped when it ribbons off your spatula. The batter, when lifted with a spatula, should keep flowing off the spatula in ribbon shapes nonstop, without drizzling off too quickly. If it is coming off in large V shaped chunks it needs to be folded more. Another test is the figure 8 test: If you can lift some batter up and use it to draw several figure 8’s without the stream breaking, it is ready!
7. Add batter to a piping bag with a medium to large sized round tip (I recommend a large 1/2-inch top). Pipe 1 to 1 ½-inch small circles of batter onto the prepared baking sheet. Make sure the piping bag is held straight up and perpendicular to the baking sheet.
8. After you’ve piped all the macarons, gently tap the baking sheet multiple times against the counter to remove any air bubbles from the macarons. If some air bubbles still remain, use a tooth pick to gently poke them out.
9. Preheat oven to 300°F. While the oven is preheating, allow the macarons to sit and form a “skin”. This “skin” should form anywhere from 8 minutes to an hour. You know the macarons are ready to be baked when you can touch them lightly without having the batter stick to your finger. Keep checking them periodically to see if they have formed a skin.
10. Bake for 15-20 minutes. Check at 15 minutes, and if they are not ready then keep checking every minute. The macarons are ready when the tops are firm and do not move around their base at all. Allow the macarons to cool completely before attempting to remove them from the silicone mat.

Make the pistachio white chocolate ganache filling:

1. Add the chopped white chocolate and pistachio paste (or cream or spread) into a heat-proof bowl and set aside.
2. In a small saucepan, heat the heavy cream over medium heat. Bring to a simmer, then pour the cream over the white chocolate mixture and lightly stir. Let it to sit for 2 minutes to allow the chocolate to melt.
3. Whisk the ganache until it comes together and is smooth. 
4. Cover with plastic cling wrap and let it cool to just warmer than room temperature before using (about 1 hour). You can cool it faster in the fridge, but keep a close eye on it by checking it regularly and stirring intermittently to prevent the ganache from cooling too fast and hardening too much.

Decorate the macaron tops:

1. Melt the white chocolate in a double broiler or in the microwave.
   • On the stove: Bring 2 inches of water to a low simmer in a saucepan over medium-low heat. Then, turn the heat to low and place a medium heatproof bowl on the mouth of the pot. Make sure that there is a gap of a few inches in between the bottom of the bowl and the water (You can also place a bowl on a steamer attachment on top of your pot). Add the chocolate and stir constantly as it melts. Stir until the chocolate is completely smooth and melted. This should take a few minutes.
   • In the microwave: Place a medium heatproof bowl of chocolate into the microwave and microwave in 30 second intervals. Remove the bowl at each interval and stir well. Repeat until the chocolate has completely melted. Stir until completely smooth.
2. Drizzle the tops of half of the macarons with the melted white chocolate, then sprinkle with chopped pistachios. Set aside to harden.

Assemble the macarons:

1. Place the cooled ganache into a piping bag fitted with a large ½ inch round tip.
2. Pipe the ganache onto the bottom half of the macaron shells (undecorated half).
3. Top each bottom half with the decorated macaron tops.
4. Place into the fridge overnight to mature and meld together.