The fish is boiled for 10 minutes, if tin is not necessary. Peel the potatoes, cut into cubes and fry. Onions cut washers and also fry. In a pan mix the fish, potatoes and onions, already prepared in this manner. Prepare Béchamel or use ready. Add salt, pepper and cream, everything to a boil over low heat. Pour over mixture and sprinkle with breadcrumbs or grated dry cheese. Bake until gilding. Garnish with olives and lettuce salad.