Preheat oven to 180 degrees. Line 12 muffin tins with cupcake papers.
Melt the butter and chocolate together in a large saucepan or in short bursts in the microwave.
In a bowl beat the eggs with the sugar and vanilla.
Sift the flour into another bowl and add the salt.
Let the chocolate mixture cool a bit before beating in the egg and sugar mixture, and then the nuts, white choc chips and flour.
Fill cupcake liners about 3/4 full with mixture and bake for around 20 minutes.
When it’s ready the top should be dried to a pale brown but the middle still dark and slightly gooey.