METHOD
Preheat oven to 220°C fan bake.
Melt butter in a pot and when it begins to foam add the flour. Stir for about a minute and add in mustard powder and nutmeg. Gradually whisk in milk, stirring constantly, until a thick, smooth sauce is produced. Season to taste.
Stir in the smoked fish, parsley and chopped boiled eggs. Place in an ovenproof dish. Top with mashed potato and grated cheese. Bake for 25-30 minutes, or until sauce is bubbling and potato is golden.