The chocolate ganache filling needs about 2 hours to set, so I recommend making it first! It can also be made up to a week in advance.

Place 120g of 63% dark chocolate and 20g of unsalted butter in a medium-sized bowl and set aside.

Pour 120g heavy cream into a heat-proof bowl and heat in 15-second intervals in the microwave until it just begins to bubble.

Pour the heavy cream over the chocolate and butter. Let the mixture sit for a couple of minutes.

Use an immersion blender or a spoon to mix the ganache until the mixture has come together and is smooth.

Press a piece of plastic wrap flush against the ganache to prevent skin from forming. Set the bowl aside to let the ganache come to room temperature and thicken.

Line two large baking sheets with parchment paper or silicon mats. Set aside.

Pour 110g of aged egg whites into the bowl of a stand mixer with a whisk and mix on medium speed until the surface of the egg whites is covered in small bubbles.

Add in a pinch of cream of tartar and continue to mix until it reaches the soft peak stage.

Gradually add 110g of granulated sugar into the eggs and mix on a medium speed for 30 seconds. Increase the mixing speed to a medium-high speed. Keep mixing until stiff, glossy peaks form.

Sift 126g superfine almond flour, 126g powdered sugar, and 14g of dark cocoa powder into the meringue, then fold the ingredients together with a rubber spatula.

Fold until a thick ribbon of batter runs off the spatula when it is lifted.

Pour the batter into a large piping bag fit with a medium-sized round piping tip and pipe 1 ¾-inch rounds on the prepared baking sheets.

Let the macarons rest for 30 minutes, or until they develop a skin.

Preheat the oven to 315 F / 157 C.

Bake one tray of macarons at a time for 19-23 minutes and rotate the pan halfway through.

Remove the pan from the oven and let the macarons cool on the pan for about 15 minutes.

Place the room-temperature ganache in a small piping bag fit with a large round piping tip.

Pair up the shells, then pipe a swirl of dark chocolate ganache on one macaron shell. Gently press a second shell on top of the ganache to create a sandwich.

Place the finished macarons in the fridge in an airtight container to mature overnight.