Line an upside down pan with a silicone baking mat and fit a piping bag with a small round tip, set them both aside.
In a medium bowl, scale the almond meal and powdered sugar. Sift both of them into a larger bowl and discard any large pieces. Set aside.
120 grams powdered sugar, 138 grams blanched almond meal, 8 grams black cocoa powder
In a stand mixing bowl, add the egg whites and begin whisking on low speed (speed 2-3) for 1-2 minutes. When the whites get foamy, add the cream of tartar.
107 grams egg whites, room temperature, ¼ teaspoon cream of tartar
Very slowly, begin adding the sugar by the spoonful, sprinkling it into the whites as they whip. When all of the sugar is added increase the speed to medium (speed 4) and whip for about 7-8 minutes or until stiff peaks form.
110 grams granulated sugar
Add the stiff white meringue to a large bowl.
Add ⅓ of the sifted dry mixture to the whites. Fold very gently with a rubber spatula until combined. The add the next ⅓ and fold to combine. Continue until all of the dry ingredients are incorporated.
Using your rubber spatula, 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 ribbons. Try to make a figure 8 with the batter. If it falls without breaking, its ready.
Fill your piping bag with the batter. Pipe directly over the top of the baking tray. When the pan is full, drop the pan on the counter a few times to release any air bubbles. Use a tooth pick to pop any bubbles that come to the surface.
Allow the shells to sit out to dry and form a skin. This can take anywhere from 30 minutes to an hour depending on the level of humidity in your house. They are ready to bake when the shell can be touched without it sticking to your finger or leaving an impression.
While the shells rest, preheat your oven to 300. (If your oven in on the hotter side, lower temperature might be better ie: 275-285)
Bake each tray for about 12-14 minutes. They are done baking when you can gently touch the top of the shell and it barely budges from the foot. Let the tray cool completely on a wire rack before removing the shells and filling.