Sift together the almond flour, powdered sugar, and cocoa powder three times to remove any lumps. Set aside. Line two baking sheets with parchment paper or silicone mats.

In a clean, dry bowl, beat the aged egg whites and cream of tartar on medium speed until foamy. Gradually add granulated sugar one tablespoon at a time, then increase speed to high and beat until stiff, glossy peaks form, about 3-4 minutes.

Fold the dry ingredients into the meringue in three additions using a flexible spatula. Use a folding and pressing motion against the bowl to deflate the batter slightly. Continue macaronage until the batter flows like lava and a ribbon disappears back into itself within 10-15 seconds.

Transfer batter to a piping bag fitted with a round tip. Pipe 1.5-inch circles onto prepared sheets, spacing them 2 inches apart. Tap the sheets firmly on the counter 5-6 times to release air bubbles.

Let piped shells rest at room temperature for 30-60 minutes until a dry skin forms that doesn't stick when lightly touched. Preheat oven to 300°F during the last 15 minutes of resting time.

Bake one sheet at a time for 15-17 minutes, rotating halfway through, until shells are set and don't wiggle when touched. The feet should be fully developed and the tops matte. Cool completely on the baking sheet.

For the ganache, heat heavy cream in a small saucepan until just simmering. Pour over chopped chocolate and let sit for 1 minute, then stir until completely smooth. Stir in butter until incorporated. Let cool to room temperature, then refrigerate for 30 minutes.

Beat the cooled ganache with a hand mixer for 30-60 seconds until fluffy and lightened in color. Transfer to a piping bag and pipe a generous amount onto half the macaron shells. Sandwich with remaining shells, pressing gently.

Refrigerate assembled macarons in an airtight container for 24 hours before serving to allow the flavors to meld and achieve the perfect texture. Bring to room temperature 15 minutes before eating.