Cod with Caviar Sauce

Name: Cod with Caviar Sauce
Ingredients: 1 Onion; 1 bunch Soup vegetables (carrot, leek, parsnip) (small, such as carrot, leek, parsnip or other aromatic vegetables such as celery or onion); 30 grams Butter; 4 Cod cutlets (each about 12o grams, from tail part); Salt; freshly ground Pepper; 1 tablespoon Lemon juice; 1 teaspoon grainy Vegetable broth; 200 milliliters Fish stock (from a jar); 50 milliliters Noilly Prat (dry vermouth); 100 grams Double cream; 20 grams Beluga caviar; 1 stalk Leek; Dill tips