Preheat the oven to 200C/400F/Gas 6.
Melt the butter in a large pan over a medium heat. Add all of the apples, the sugar and vanilla seeds. Cook until the apples become soft enough to break down into a purée. Remove from the heat and allow to cool.
Once the apple mixture is cool, add the egg yolk and mix well to combine.
Butter the bread slices and line a 600ml/1 pint pudding basin with some of the bread slices, overlapping the slices to ensure there are no gaps.
Spoon in the apple mixture and cover the top with the remaining bread.
Place a plate on top of the pudding and weigh it down with a can of beans (or similar weight) for one hour.
Remove the plate and cover the pudding with kitchen foil. Bake in the oven for 30 minutes.
Remove the foil and bake for ten more minutes, or until the top is light golden-brown.
For the sauce, place the butter, sugar and cream into a separate pan over a medium heat. Bring to the boil and cook for 5-6 minutes, until combined as a smooth sauce.
To serve, cut out a wedge of apple Charlotte and place onto each plate. Add a generous spoonful of the sauce and a spoonful of clotted cream alongside.