Preheat the oven to 180C/360F/Gas 4.
Butter a 1½ litre/2 pints 12¾fl oz ovenproof dish with half of the butter.
Spread the bread slices with the remaining butter on both sides. Cut the bread into triangles and overlap layers of bread with the sultanas in the greased dish.
Beat the egg yolks, whole eggs and sugar together in a large bowl until creamy. Beat in the cream, milk, vanilla extract and Irish cream liqueur.
Pour the mixture over the bread, and press down the bread slices until submerged. Leave to stand for 20 minutes to allow the bread to soak up the liquid.
Place the dish into a roasting tray and add enough water to come halfway up the dish (this is called a bain-marie). Sprinkle with demerara sugar and bake for 35-40 minutes until golden-brown.
To serve, place a portion of bread and butter pudding on each plate and pour over the double cream.
