A Very Chocolatey Mousse

1 tbsp cocoa powder
140g vanilla sugar
3 whole eggs, separated, plus 3 extra egg yolks
200ml double cream
85g unsalted butter, cubed
225g dark chocolate, broken into pieces
1 tbsp armagnac

To decorate
125ml double cream, lightly whipped
50g dark chocolate, grated

Put 55g of the sugar, all 6 egg yolks, the cocoa powder and the cream together in a bowl and set the bowl over a saucepan of simmering water.

Whisk the mixture continuously until it thickens enough to coat the back of a wooden spoon.

Remove from the heat and add the butter and chocolate pieces, a little at a time, whisking until melted and fully incorporated.

Stir in the armagnac.

Whisk the egg whites until frothy. Add the remaining sugar a little at a time, and continue to whisk until the mixture is thick and glossy and meringue-like.

Fold the meringue lightly but thoroughly into the chocolate mixture.

Spoon the mixture into a large serving bowl or individual glasses and refrigerate until set.

Decorate with a swirl of whipped cream and some grated chocolate.