Easy chocolate mousse

Method

1. Put the chocolate, rum and butter in a mixing bowl set over a pan of steaming but not simmering water (don’t let the water touch the pan). Allow to melt until completely smooth, then remove from the heat and leave to cool to just above room temperature.
2. While it’s melting, put the egg yolks in a mixing bowl with the sugar and whisk with an electric mixer until pale and moussey, and the mixture leaves a trail from the whisk when raised. Once the chocolate has cooled, gently mix it into the yolk mixture using a metal spoon or balloon whisk.
3. Put the egg whites into a large, spotlessly clean mixing bowl and whisk with clean beaters until they form medium-stiff peaks. Fold a large spoonful of the whites into the chocolate mixture using a metal spoon or balloon whisk. Once combined, carefully fold the remaining whites through in 3 batches, trying not to knock out any air from the mixture. Gently divide the mixture between ramekins, then chill for 2-3 hours or overnight until set. Bring the mousses out of the fridge 30 minutes before serving to take the chill off them.