Dark chocolate mousse with blood orange gel and hazelnut crumb

Method

1. Melt the dark and milk chocolate and the butter in a bowl set over a pan of simmering water (don’t let the bowl touch the water). Meanwhile, whisk the egg yolks with the sugar in a bowl until pale and creamy. In a separate bowl, use a hand mixer to whisk the egg whites with the lemon juice until they form stiff peaks (they shouldn’t flop over when the whisk is removed).
2. Stir the melted chocolate and a pinch of salt flakes into the egg yolk mixture. Fold in the egg whites using a large metal spoon, adding roughly a quarter of the mixture at a time and using a chopping and folding method to keep as much of the air in the egg whites as possible. Cover the bowl and transfer to the fridge for at least 4 hours.
3. To make the gel, put the orange juice and sugar in a small pan, then bring to the boil. Whisk in the agar agar, simmer for 5 minutes, then put in a container and chill for 1 hour. Once set, whizz the jelly in a blender until smooth. Transfer to a small squeezy bottle or piping bag and keep in the fridge until needed.
4. For the crumb, put all the ingredients in a food processor or blender and pulse to a rubbly crumb (some texture is good; it doesn’t need to be super fine).
5. To serve, spread a spoonful of the crumb into a rough circle on the centre of each plate. Prepare a tall glass or jug of hot water and dip a large dessert spoon into it. Dry the warmed spoon, then scoop a neat, smooth rocher (an oval shape) from the bowl of mousse and place it on top of the crumbs. Sprinkle with a few more salt flakes, then pipe different size dots of the blood orange gel around the plate. Finish with a sprinkling of orange zest.