Prepare Egg Whites: Separate egg whites from yolks and let them come to room temperature, about 30 minutes. Whip egg whites until foamy, gradually adding sugar, salt, and cream of tartar until stiff peaks form.

Mix Dry Ingredients: Sift together confectioners' sugar, almond flour, cocoa powder, and instant coffee. Sift at least twice to ensure a smooth texture.

Combine Mixtures: Fold dry ingredients into egg whites carefully. Stop folding once the mixture flows like thick lava and forms a ribbon, about 40-50 folds.

Pipe and Rest: Pipe 1½-inch rounds onto baking sheets. Tap firmly to release air bubbles and let the shells rest for 30-45 minutes.

Bake: Preheat oven to 300°F (150°C). Bake macarons for 20 minutes, rotating trays halfway through. Let cool completely.

Make Ganache: Heat heavy cream, instant coffee, and salt until bubbling. Pour over chocolate and butter, whisk until smooth, then cool until pipeable.

Assemble Macarons: Pair macaron shells and pipe ganache onto half. Sandwich with remaining shells.

Decorate: Drizzle melted chocolate over macarons and sprinkle with crushed peppermint. Let decorations set before serving.