- Preheat the oven to 180ºC fan/200ºC/gas 6. Grease and line a 28 x 18cm deep baking tray.
- Put the butter in a small pan and gently melt. Gently melt the block of chocolate in a bowl over a pan of hot water. No need to even simmer, as white chocolate easily melts.
- Put the eggs and sugar in a bowl and whisk well until they begin to look thick and pale.
- Add the chocolate and melted butter and whisk thoroughly.
- Add the vanilla, chocolate chips, flour and nuts and stir well. Pour into the prepared tin.
- Bake in the oven for 30 minutes. The mixture will have risen but will go down when taken out of the oven.
