Bring the milk, lemon zest, sugar and the vanilla bean to a boil slowly in a pot.
Take off the heat and remove the vanilla, allowing the milk to cool.
In another pot, melt the butter until it foams and then add the flour, stirring with a whisk until the foam becomes golden in colour.
Add the warm milk whilst continuously stirring and whisk over a low heat until the mixture thickens.
Take off the heat and whisk in the egg yolks so that everything is well combined.
Pour into a shallow, buttered dish and put in the fridge for a minimum of four hours.
Cut this cold custard into squares or triangles.
Beat the egg well (as you would for French toast
) and dip the pieces of set custard
in this and then into the breadcrumbs.
Heat the oil in a deep pan and fry the slices in batches until they are golden brown.
Take out of the oil, drain quickly on paper towels and dredge the warm slices in the cinnamon sugar.
Serve lukewarm or cold.