Directions
1-Separate 4 large eggs into two bowls,: Separate 4 large eggs into two bowls, yolks in one, whites in another, then leave them to come to room temp for 10-15 mins (room temp eggs whip better).
2-Gently melt 200g dark chocolate and 50g: Gently melt 200g dark chocolate and 50g unsalted butter in a heatproof bowl over simmering water, stirring until smooth, dont let the bowl touch the water or any steam get in; or microwave in 20 second bursts stirring between each.
3-Whisk the 4 egg yolks with 2: Whisk the 4 egg yolks with 2 tbsp caster sugar until pale and slightly thickened, about 2-3 minutes with an electric whisk.
4-Temper the yolks by adding a spoonful: Temper the yolks by adding a spoonful of the hot melted chocolate into the yolks, stir to combine, then fold in the rest of the chocolate until silky and even.
5-Whip 300ml double cream with 1 tsp: Whip 300ml double cream with 1 tsp vanilla extract to soft peaks, dont overwhip it into butter.
6-Whisk the egg whites with a pinch: Whisk the egg whites with a pinch of fine sea salt until they hold soft to medium peaks, not dry.
7-Fold the whipped cream into the chocolate-yolk: Fold the whipped cream into the chocolate-yolk mix gently until mostly combined, then fold in the egg whites in two additions using a spatula, keeping as much air as possible.
8-Spoon or pipe the mousse into serving: Spoon or pipe the mousse into serving glasses or bowls, tap lightly to remove big air pockets.
9-Chill for at least 2 hours or: Chill for at least 2 hours or until set, then dust with cocoa powder before serving.