Line an upside down pan with a silicone baking mat and fit a piping bag with a small #12 Wilton round tip, then set them both aside.
In a medium bowl, sift the almond meal, powdered sugar, and cocoa powder into a larger bowl and discard any large pieces. Set aside.
120 grams powdered sugar, 138 grams blanched almond meal, 8 grams dark cocoa powder
In a stand mixing bowl, begin whisking the egg whties on medium low speed (speed 3-4) for 2-3 minutes until foamy, then add the cream of tartar.
⅛ teaspoon cream of tartar, 102 grams egg whites, room temperature
Very slowly, sprinkle the sugar into the mixing whites with a spoon. When all of the sugar is added, increase the speed to medium (speed 4-5) and whip for about 6-7 minutes or until stiff peaks form.
110 grams granulated sugar
Add ⅓ of the sifted dry mixture to the bowl of meringue. Fold very gently with a spatula until combined. Continue until all of the dry ingredients are incorporated.
Scrape the batter against the side of the bowl. Every few scrapes, pick up the batter and let it fall into the bowl. The batter should flow slowly in a continuous ribbon. Try to make a figure 8 with the batter. If it falls without breaking, it's ready.
Pipe the batter directly over the baking tray. Drop the pan on the counter a few times to release any air bubbles which you can pop with a tooth pick. Sprinkle the tops of the shells with some pistachio crumbs.
Let the shells sit to dry and form a skin, at least 30 minutes or until you can touch the tops without leaving an impression. Preheat the oven to 300 F/149 C.
Bake for 12-14 minutes. The shells are done baking when the top of the shell doesn't budge from the feet. Let the tray cool completely before removing.