1. Combine the almond flour, powdered sugar, and Oreo crumbs. Sift everything together to remove lumps, then set aside.
2. In a clean mixing bowl, whip the egg whites until foamy. Slowly sprinkle in the granulated sugar while mixing. Add the food coloring and continue whipping until the meringue holds firm, glossy peaks.
3. Add the dry ingredients to the meringue in three stages. Fold gently after each addition, scraping the bowl as you go. Stop once the batter flows smoothly and slowly off the spatula—think molten lava, not cake batter.
4. Spoon the batter into a piping bag fitted with a round tip. Pipe small oval or egg-shaped rounds onto a lined baking sheet. Firmly tap the tray on the counter several times to pop hidden air bubbles.
5. Let the piped shells rest uncovered for 30–40 minutes, or until the tops feel dry to the touch. This step is key for forming those classic macaron feet.
6. Warm the heavy cream until just beginning to steam. Pour it over the chopped dark chocolate along with the salt and espresso powder. Let sit for one minute, then stir until silky and smooth.
7. Leave the ganache at room temperature until thick enough to pipe or spread.
8. Preheat the oven to 285°F (140°C). Bake the shells for 18–20 minutes, rotating the tray once if needed. They should be set but still pale.
9. Cool completely on the baking sheet before removing.
10. Pipe or spoon ganache onto half of the shells, then sandwich with the remaining shells.
11. Refrigerate the filled macarons for at least 12 hours before serving. Bring to room temperature for the best texture and flavor.
