Dark chocolate mousse with crème fraîche

Break the chocolate into a mixing bowl, then add the butter. Set over a pan of barely simmering water, making sure the water doesn’t touch the bowl. Leave to melt, then stir together. Set the bowl aside to cool to room temperature (dip in a clean finger to test the chocolate no longer feels hot to touch).

Add the egg yolks, 50g sugar and rum to a second mixing bowl. Place over the pan of simmering water and whisk vigorously for 30-45 seconds. Remove from the heat and whisk for 2 minutes more until pale and voluminous, like runny mayonnaise, and not grainy. Set aside.

Using a third mixing bowl and a clean whisk, whisk the egg whites and a pinch of salt to a soft peak. Sprinkle over 1 tsp sugar, then whisk the whites to stiff peaks.

Combine the egg yolk and chocolate mixtures in whichever of the bowls is largest. Fold one-third egg white into the mix, then quickly fold in the rest until the mix is no longer streaky.

Divide the mix between 6 small (90-120ml) glasses, then cover and chill for 2 hours or more. Remove from the fridge 20-30 minutes before you plan to serve. When you do, top each with a dollop of chilled crème fraîche and a grating of extra chocolate.