Potato, Spinach and Fish Casserole

Ingredients

• 1 clove garlic, finely chopped 

• 2 tablespoons (30 ml) butter
• 8 cups (2 litres) firmly packed spinach
• Salt and pepper
• 3 tablespoons (45 ml) butter
• 3 tablespoons (45 ml) unbleached all-purpose flour
• 2 cups (500 ml) milk
• A pinch nutmeg
• 4 cups (1 litre) potatoes, peeled and thinly sliced on a mandolin
• 1 lb (454 g) skinless sole fillets or other thin fish fillets
• 1 1/2 cups (375 ml) grated cheese of your choice (Gruyère , mozzarella, provolone, etc.).