Start this recipe by melting the milk chocolate in a heatproof bowl set over a pan of simmering water. Whisk the egg yolks, vanilla essence and the caster sugar in a heatproof bowl over a pan of simmering water with a hand-held electric blender for about 3 minutes until the mixture is pale and foaming. Remove the bowl from the heat and keep whisking, adding the melted chocolate. Leave to cool for a few minutes, then carefully fold in the whipped cream. Quickly whisk egg whites to soft peaks, then carefully fold the egg whites into the chocolate mixture so you don’t knock out too much air. Place a half of the fresh raspberries in the base of your serving glasses then spoon over the white chocolate mousse. Allow to chill for 2 hours. Meanwhile, you can make the sesame seed brittle. Pour the sugar and 4 tablespoons of water into a clean pan. Mix with a spoon then place on heat and cook till lightly golden. Add in the sesame seeds and continue to cook till golden brown. Quickly remove off the heat and pour the mixture onto an oiled baking sheet to stop it from sticking. Even out with a palette knife and allow to dry for 15 minutes. When ready, break the sesame brittle up into pieces and serve stuck into the white chocolate mousse. Decorate with crushed pistachios and the remaining raspberries