Toast the walnuts in a small dry pan until they are golden and start to release their gorgeous aroma, keep an eye on them and don’t let them burn!
Whizz the toasted walnuts in food processor or pound to a powder.
Break up the mixture of dark and milk chocolate and melt this in a bain-marie (bowl set above a pan of simmering water) or in the microwave if you have one.
Once melted remove from the heat and stir in chopped butter until everything is completely mixed.
Now add the Guinness, pinch of salt and the vanilla extract. Stir well to make sure everything is incorporated into a rich smooth sauce.
Add the blitzed walnuts and stir thoroughly.
Spoon this mixture into a sterilised glass or jar and set aside while you make the topping.
Melt the white chocolate in the same way you did the other type and remove from heat before stirring in the cream and vanilla extract.
Spoon this on top of the dark chocolate mixture in the glass or jar and leave it all to set and settle overnight. This also allows the flavours to really develop.