Drain fava beans and rinse them under cold running water. Transfer beans to a large saucepan or soup pot with enough cold water to cover. Bring to a boil, reduce heat to simmering and cook until tender, 1 to 1-1/2 hours. Skim foam from surface and add more water, if needed. Add salt, to taste, in last 1/2 hour of cooking. Remove from heat and allow beans to cool in their liquid at least 30 minutes.
In a large skillet heat oil over medium heat and add chorizo, onion and green pepper. Saute, stirring and breaking up sausage, until browned and onion is tender, 5 to 7 minutes. Add parsley, garlic, red pepper flakes and drained fava beans. Cook, stirring, 1 minute. Stir in tomato sauce and 4 cups water; season to taste with salt and pepper. Bring to a boil, cover and reduce heat to simmering. Cook, stirring once or twice, until flavors are combined and beans are very tender, 25 to 30 minutes.
Yield: 4 to 6 servings