Grease the dish or basin. Sift the flour, salt, sugar, baking powder and cocoa into a bowl. Combine the butter, egg and vanilla, then add the nuts. Pour this into the pie dish, cover with cling film and put in fridge overnight to set. Preheat the oven to 180c, gas mark 4. Sprinkle the sugar and cocoa over the pudding and pour boiling water over the top. Put into the oven and cook for 45 mins, until puffy and firm in the centre. Remove and serve with pouring cream and ice cream.