With the rack in the middle position, preheat the oven to 180 °C (350 °F).
In a large non-stick skillet or wok, soften the garlic in the butter. Add the spinach and stir until just wilted. Season with salt and pepper. Drain well. Set aside.
In a small saucepan, melt the butter. Add the flour and cook for 1 minute, stirring constantly. Add the milk and nutmeg and bring to a boil, stirring constantly. Simmer gently for about 2 minutes. Season with salt and pepper. Set aside.
In a 2 litres (8 cups) baking dish, spread one third of the potatoes. Layer with half the spinach and cover with a third of the béchamel sauce. Add one third of the potatoes and layer with the fish. Season with salt and pepper. Layer with the remaining spinach and cover with one third of the béchamel sauce. Top with the remaining potatoes and béchamel sauce. Sprinkle with the cheese.
Bake for about 1 hour and 15 minutes or until the potatoes are tender. If desired, brown under the broiler. Let stand for 10 minutes and serve with a green salad.
Perfect for Sunday cooking.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.