Gather the ingredients. For this recipe, be careful with the wording, as you mix many different things and then later incorporate them in an order.
Separate 3 eggs whites and yolks while eggs are cold. Place whites in a large bowl and yolks in a small bowl.
The Mixes
Chocolate Mix: Heat some water on in a cooking pot. Place a mixing bowl over it. Break 125 g dark chocolate into pieces and place in the pot with 10 g unsalted butter. Stir slowly until its fully melted and smooth.
Cream Mix: In a mixing bowl, beat 1/2 cup heavy cream until stiff peaks form, being careful not to over-whip.Egg White mix: In the bowl with egg whites, add 3 Tbsp. sugar. Beat whites until firm peaks form.Egg Yolk Mix: In the yolks bowl, whisk the yolks until uniform.
The Mousse
Fold Egg Yolks Mix into the Cream Mix using a rubber spatula - 8 folds max.Pour Chocolate Mix into Egg Yolk Cream Mix. The chocolate mix should still be runny but warm (95-104℉). If too cool or thick, microwave in burst of 5 seconds at a time until runny. Fold through - 8 folds max.
Pour Egg Whites Mix into Chocolate Egg Yolk Cream Mix. Fold through until incorporated and no more white lumps remain - aim for 20 folds, but ensure there are no obvious egg white patches.
Divide mixture between 12 small pots (or the separation of your choice). Refrigerate for at least 6 hours, preferably overnight.
The Serving
To serve, garnish with 50 g dark chocolate. Best served alongside a cup of coffee or tea for a delightful treat.