Finely chop the dark chocolate and place it in a heatproof bowl. Heat the heavy cream until it simmers, pour it over the chocolate, and let sit for 5 minutes. Stir until smooth and set aside to cool.

In a medium mixing bowl, combine the almond flour, powdered sugar, and cocoa powder. Sift these dry ingredients together to eliminate lumps and set aside.

In a stand mixer, whisk the aged egg whites at medium speed until foamy. Add cream of tartar, then gradually add granulated sugar, whipping until stiff peaks form (5-7 minutes).

Fold the sifted dry ingredients into the whipped egg whites gently until the batter reaches a flowing lava consistency.

Transfer the batter to a piping bag and pipe 1-inch circles on lined baking sheets. Tap to release air bubbles and let rest for 30-45 minutes.

Preheat oven to 300°F (150°C). Bake macarons for 13-15 minutes until tops are firm and feet are slightly puffed. Let cool completely before removing.

Pair macaron shells by size. Spoon ganache onto one shell, top with Swiss meringue, then place another shell on top. Garnish with mini marshmallows if desired.

Place assembled macarons in an airtight container and refrigerate for 12-24 hours before serving to enhance flavors.