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 (this usually takes me about 45 seconds). If you don't have a microwave, heat the cream over a medium-high heat in a saucepan until it starts to bubble and steam.

Pour the heavy cream over the chocolate and butter. Make sure all the chocolate is submerged beneath the cream. Let the mixture sit for a couple 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 a 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 a 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 where you can see the whisk leaving faint tracks in the egg whites.

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. Use a circular motion that sweeps around the edge of the bowl and then pull through the bottom of the bowl to make sure everything is getting mixed together.

Fold until a thick ribbon of batter runs off the spatula when it is lifted. You should be able to draw a couple figure 8's with the batter running off your spatula when it is the right consistency. If the stream of batter breaks before you're able to do this, you may need to stir it a bit more.

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, spacing them about 1-inch apart.

Pipe one pan at a time and bang the pan firmly on the counter a few times to release air bubbles, then pop any remaining air bubbles that come to the surface with a toothpick.

Let the macarons rest for 30 minutes, or until they develop a skin. The macarons should look matte once the skin has formed. While the macarons rest, preheat the oven to 315 F / 157 C.

Bake one tray of macarons at a time on the middle rack of your oven for 19-23 minutes and rotate the pan halfway through to help them bake evenly. I find that chocolate shells always take a couple minutes longer to bake than my regular shells.

Remove the pan from the oven and let the macarons cool on the pan (about 15 minutes), then gently remove them from the silpat mat.

Place the room temperature ganache in a small piping bag fit with a large round piping tip. It should be thick enough to scoop into the piping bag and hold its shape. If it is too thick to pipe, submerge the piping bag in a bowl of warm water to make it easier to pipe.

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.

If desired, drizzle some melted chocolate on top of each macaron.

Place the finished macarons in the fridge in an airtight container to mature overnight. When you're ready to enjoy them, let them sit at room temperature for 10-20 minutes and enjoy!