Start by preheating your oven to 300°F/150°C. If you have a fan oven then switch it off.
Sift the powdered sugar into a large bowl. Sift the almond flour on top and then combine the two.
Beat the egg whites until foamy.
Add cream of tartar, salt and espresso powder. Mix for 1 minute and then add the sugar.
Beat the mix for 5 minutes or until peaks form.
Fold the mix into the egg whites with a large spatula, but be careful not to over mix. The batter should resemble molten lava. Don’t allow it to become too thin.
Tightly twist the bottom of a pastry bag and pour in the batter. Use a circular piping tip of about half an inch in diameter and pipe out 1-inch mounds onto ungreased parchment/baking paper.
Lightly sprinkle some coffee grounds on top of each mound.
Leave the mounds to sit at room temperature for 30 minutes or until they start to form a skin that’s slightly sticky to the touch and not fully dry. Note that this might take longer depending on the humidity of your room.
Bake 1 try at a time for 15-20 minutes. If they’re underbaked then they will stick to the parchment/baking paper. Make sure you remember to bake the second tray for a minute or two less.
While the macarons cook, over medium-high heat, heat up the heavy cream in a saucepan until it starts to come to a very slight boil.
Put the chocolate chips in a bowl and submerge them with the hot cream. Allow the chocolayte to sit for a few minutes then stir until it forms a smooth and creamy consistency.
Fill a piping bag with the chocolate mix and snip the tip.
Ensure the inside face of the newly baked cookies are facing up, and pipe a small mound of chocolate mix onto one of every pair of cookies to form the filling. Then place the other baked cookie on top to create your macaron.