Preheat the oven to 350 degrees F.

Grease an oven-proof casserole dish or a shallow baking dish with the capacity of about 1½-quarts with some of the butter.

Put the raisins in a small bowl, pour the rum over, and microwave for 30 seconds, then leave to stand. This is a good way to rehydrate them quickly.

Make the sandwiches with the brown bread, butter and ginger jam (2 tablespoonfuls in each sandwich); you should have some butter left over to smear the top later. Now cut the sandwiches in half into triangles and arrange them evenly along the middle of the dish. Place one triangle in the dish with the point-side up, the next one with the point side down, and so on. Squeeze a sandwich-triangle down each side, as needed. Sprinkle with the raisins and unabsorbed rum that remains in the bowl.

Whisk the egg yolks and egg together with the sugar, and mix in the cream and milk. Pour this over the triangles of bread and leave them to soak up the liquid for about 10 minutes, by which time the pudding is ready to go into the oven. Smear the bread crusts that are poking out of the custard with the soft butter, mix the ground ginger and Demerara sugar together and sprinkle this mixture on your buttered crusts and then lightly over the rest of the pudding.

Sit the pudding dish on a baking sheet and put in the oven to cook for about 45 minutes or until the custard has set and puffed up slightly. Remove, let sit for 10 minutes – by which time the puffiness will have deflated somewhat – and spoon out into bowls, putting a pitcher of custard, should you wish, on the table to be served alongside.