Line two large baking sheets with silicone mats or parchment paper. Set aside.
Use a food processor to finely grind 35g of pistachios. The mixture should look dry. Stop mixing if the pistachios begin to release oil and look wet. Sift the pistachios through a fine mesh sieve. Set aside.
Pour 110g of aged egg whites into the bowl of a stand mixer with a whisk and mix on medium speed until the surface of the egg whites is covered in small bubbles. Add in a pinch of cream of tartar and continue to mix until the mixture has soft peaks.
Gradually mix 110g of granulated sugar into the eggs over a few minutes while mixing on a medium-low speed (speed 4 on a KitchenAid). Then increase the mixing speed to a medium-high speed (speed 6 on a KitchenAid). Keep mixing until stiff, glossy peaks form.
Sift 105g of superfine almond flour, 125g of powdered sugar, and 35g of finely chopped pistachios into the meringue. If you're a little bit short on ground pistachios (sometimes large chunks can't be sifted and you lose some in the process), add in additional almond flour to make up the difference.
If desired, add a small squirt of neon green gel food coloring to brighten up the green color of the shells, then fold the ingredients together with a rubber spatula. Use a circular motion that sweeps around the edge of the bowl and then pulls through the bottom of the bowl to make sure everything is getting mixed together.
Fold until a thick ribbon of batter runs off the spatula when it is lifted. You should be able to draw a couple of figure 8s with the batter running off your spatula when it is the right consistency. If the stream of batter breaks before you're able to do this, you may need to stir it a bit more.
Pour the batter into a large piping bag fitted with a medium-sized round piping tip and pipe 1 1/2-inch rounds on the prepared baking sheets, spacing them about 1 inch apart.
Bang the pans firmly on the counter a few times to release air bubbles, then pop any remaining air bubbles that come to the surface with a toothpick.
Let the macarons rest for 30 minutes, or until they develop a skin. The macarons should look matte once the skin has formed. While the macarons rest, preheat the oven to 315°F/157°C.
Bake one tray of macarons at a time on the middle rack of your oven for 18-21 minutes and rotate the pan halfway through to help them bake evenly.
Remove the shells from the oven and let them cool fully on the pan, then gently remove them from the Silpat mat and pair them together. If you make the shells in advance, they can be stored at room temperature in an airtight container for up to 2 days. Set aside.