Fillet of fish gratin

ingredients

     1kg fillet of hake
     Salt and pepper to taste
     1 grated onion
     2 onions, sliced
     2 cloves garlic, crushed
     2 spoons (soup) of butter
     2 cups (tea) milk
     1 tbsp (tablespoons) cornstarch
     1 gem
     Nutmeg to taste
     Margarine for greasing
     2 cups (tea) of shredded mozzarella cheese
     2 cups (tea) of chopped tomatoes without seeds

How to Prepare

     Season the fish with salt, pepper, grated onion and garlic. Let rest for 10 minutes. In a saucepan, heat the butter and fry the onion slices until wilted. Mix the cornstarch dissolved in milk and egg yolk and pour into pan. Cook, stirring constantly, until thickened. Season with salt, nutmeg and pepper. In a greased refractory, arrange the fish and put the cream on top. Mix the mozzarella with tomatoes and season with salt. Sprinkle on top and bake in moderate oven, preheated for 20 minutes. Serve immediately accompanied by green salad.