Boil the chicory for 5 - 10 minutes and drain well.
In the meantime, melt the butter in a saucepan. Add the flour and mix well with the melted butter. Pour in some of the milk and stir until smooth. Pour in the rest of the milk, stirring constantly.
Add 100 g of the cheese to the milk mixture and stir well again. Season the sauce with a little salt, pepper and nutmeg. Let simmer for a few minutes and remove from heat.
Wrap each chicory with a slice of ham and place in a baking dish. Pour the sauce evenly over the vegetables. Finally sprinkle the rest of the cheese over the casserole and place the mold in the preheated oven for about 45 minutes at 180 ° C top / bottom heat.