Preheat the oven to 410°F (210°C).
Rinse and dry the cod filets. Finely chop the onions and the garlic.
Heat half the butter in a frying pan. Cook the cod filets for 2 minutes on each side.
Remove filets and place in a casserole dish. Season with nutmeg, salt and pepper.
Sprinkle the chopped onion and garlic over the seasoned filets.
Beat the eggs together with the cream.
Pour over the fish.
If you’d like, you can now sprinkle the Gouda cheese on top. The cookbook notes that it is important to use a cheese (like Gouda) that does not negate the flavor of the fish and is not stringy.
Bake 20 minutes.