Chocolate Ganache Macaron Filling
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 semi-sweet 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. Place the bowl in the fridge to chill for about 2 hours. If you make it in advance, let it chill in the fridge in a bowl and scoop it into a piping bag when you're ready to use it.
When you're ready to use this ganache, place it in a piping bag fit with a large round piping tip. It should be thick enough to scoop into the piping bag and hold its shape.
Pipe a thick dollop of 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. When you're ready to enjoy them, let them sit at room temperature for 10-20 minutes and enjoy!