For the macarons:

• Sift together the almond flour, icing sugar, and Oreo crumbs in a bowl. Set aside.
• In a separate bowl, whip the egg whites until they begin to form soft peaks. Gradually add in the granulated sugar and food colouring, and continue to whip until stiff peaks form.
• Gently fold in the almond flour mixture in three additions, being careful not to over-mix. Continue folding until the batter reaches a lava-like consistency.
• Transfer the batter to a piping bag fitted with a round tip. Pipe the batter onto the prepared baking sheet in small, egg-shaped circles. Tap the baking sheet against the counter a few times to release any air bubbles.
• Allow the macarons to rest at room temperature for 30-40 minutes, until a skin forms on the surface. This will help them develop their signature "feet" when baking.
• While the macarons rest, make the ganache. Heat the heavy cream in a saucepan over medium heat until it begins to simmer (or in the microwave). Remove from heat and add the chopped dark chocolate, sea salt, and espresso powder. Stir until the chocolate is melted and the ganache is smooth.
• Set the ganache aside to rest and thicken at room temperature.
• Preheat your oven to 285°F and line a baking sheet with silicone mats.
• Bake the macarons in the preheated oven for 18-20 minutes, until they are set but not browned. Allow them to cool completely on the baking sheet before removing.
• Once the macarons have cooled, pipe or spoon a dollop of ganache onto one half of each macaron. Top with another macaron shell to make a sandwich.
• Store the macarons in the refrigerator for at least 12 hours before serving, to allow the flavours to meld together. Bring to room temperature before serving.
• Enjoy your delicious and beautiful robin's egg blue macarons with Oreo speckles and dark chocolate ganache filling!