For the Macaron Shells:

1. 1. Preheat your oven to 300°F (150°C) and line two baking sheets with parchment paper.
2. 2. In a bowl, sift together powdered sugar, almond flour, and cocoa powder to eliminate lumps.
3. 3. In a clean bowl, whip the egg whites until frothy. Gradually add granulated sugar while continuing to whip until stiff peaks form.
4. 4. Gently fold the dry ingredients into the whipped egg whites using a spatula until just combined.
5. 5. Transfer the batter into a piping bag fitted with a round tip. Pipe small circles onto prepared sheets, leaving space between each mound.
6. 6. Bake in preheated oven for about 15-18 minutes. Allow them to cool completely on the baking sheet before transferring.

For the Ganache Filling:

1. 7. Melt dark chocolate and butter together in a microwave-safe bowl until smooth. Let it cool slightly before using as filling between two macaron shells.