Add the egg whites to a large glass or metal bowl and bring to room temperature.

Add the almond meal, powdered sugar, and salt to a food processor and pulse until it is a fine powder. Set aside.

Add the cream of tartar to the egg whites and use a whisk attachment on a hand mixer (or stand mixer) and whisk until soft peaks form. While the mixer is running, slowly add the granulated sugar, about 1-2 tablespoons at a time. Continue mixing as you add all of the sugar and beat until stiff peaks form.

Sift the dry ingredients into the egg whites. Use a spatula to gently fold the dry ingredients into the egg whites. Fold until completely incorporated and the batter runs off the spatula in long ribbons.

Line 2 baking sheets with silicon baking mats or parchment paper. Add the batter to a piping bag fitted with a round piping tip (about 1/2 inch in diameter) and pipe the batter into 1 1/2 inch circles.

Once all the rounds are piped, gently lift and drop the baking sheets onto the counter to help pop any air bubbles. Let the macaron shells sit uncovered at room temperature for 45-60 minutes to help form a dry shell on the outside.

When the shells have dried, preheat the oven to 300 degrees. Bake the shells for 10-12 minutes. When done, carefully slide the silicon mats or parchment paper onto wire racks so the macarons don't over-bake by cooling on the hot pans. Cool completely before carefully removing from the parchment paper or silicon mat. Make the ganache while the macaron shells are cooling.

Whisk together all of the ingredients in a small bowl. Whisk vigorously until no lumps of powdered sugar remain.

Transfer the icing to a piping bag and store in the fridge until ready to use.

Place the macarons in similar-sized pairs. Pipe a small dollop of icing onto the flat side of one of the macarons. Gently press another macaron on top, just until the icing reaches the edges. Transfer the macarons to an airtight container and place them in the fridge to age overnight.

Bring to room temperature before serving.