Cook potatoes in salted water until soft , drain . Mash potatoes together with 100 g butter until creamy . Add the nutmeg and fold in the cream . Taste and season ... keep warm until you need it .
In the meantime , melt 75 g of the butter in a small saucepan , add the flour and stir until it form a thick paste . Add the milk to the roux keep on stirring until you have a fabulously creamy bechamel .
Fold the parsley and garlic into the sauce and season with white pepper only .
Butter a deep ovenproof dish with the remaining butter .
Arrange the cubed fish and eggs in the dish and spoon the hot sauce over .
Top with the mash and bake 35 - 40 minutes or until potato is nicely browned .