Drain the Canned Chickpeas (15 ounce) and put 200 milliliter of the chickpea water in the bowl of a standard mixer. Add Cream of Tartar (1/4 teaspoon), Salt (1/4 teaspoon), Powdered Confectioners Sugar (1/4 cup). Beat on medium high speed for 15 minutes. After this, the liquid should have tripled in volume, and it should be able to hold stiff peaks.
Meanwhile, melt the 70% Dark Chocolate (200 gram) and Almond Milk (1/3 cup) in a double boiler or in the microwave at 30-second intervals until the chocolate is all melted. Stir to combine the mixture, then transfer it to a large mixing bowl.
Fold the whipped aquafaba into the chocolate-almond milk mixture in batches—be delicate. Transfer the chocolate mousse into small serving vessels, then transfer to the fridge to let the mousse set up — in about an hour it will start to set. Store in fridge.