* The cod steaks should be boneless and skinless, about 6 oz each. Melt 1 tablespoon of the butter in a saucepan. Add the flour and stir with a wire whisk until blended. Add the milk and cream all at once. Stir rapidly with the whisk. Bring to a boil and add the Gruyere cheese. Stir until the cheese has melted. Add the egg yolk, stirring rapidly with the whisk. Add salt, pepper, nutmeg and cayenne. Simmer, stirring, for 1 minute. Set aside, cover and keep warm. Pick over spinach and discard any tough stems. Wash spinach thoroughly to remove any sand. Put spinach in a large saucepan, add salt and cook on high heat, stirring, until wilted, about 2 minutes. Drain well and squeeze out excess moisture. Set aside and keep warm. Preheat the oven to 450 F. Grease a metal baking dish with 1 tablespoon of the butter. Scatter the shallots over the dish. neatly arrange the pieces of cod over the shallots. Season with salt and pepper. Add the wine, cover with foil and bring to a boil on top of the stove. Put the dish in the oven and bake for 5 minutes. Select a baking dish large enough to hold the fish in 1 layer. Spread the remaining 1 tablespoon of butter over the bottom of the dish. Spoon the spinach over the bottom and carefully transfer the cooked codfish over the spinach, reserving the wine liquid in the first dish. Reduce by 1/2 the wine liquid in the metal baking dish and add it to the cheese sauce. Bring to a boil stirring with a wire whisk. Spoon the hot sauce over the fish, smoothing it over to cover the fish. Sprinkle with Parmesan cheese. Turn on the broiler unit and put the dish under the broiler with the door open until nicely browned and bubbling.