I make this soup for our night crossings of The Sea of Cortez. Before leaving port, I prepare a pot of soup so we don't have to worry about dinner! A pressure cooker is great because it can also be used to hold the soup without refrigeration for several hours. I prepare the soup through step number 7, open it up and confirm that the bean are done, and then bring the pot up to pressure again, then remove from the heat. Later, when it's dinner time, I remove the lid, add the tomatoes and meat, returning the lid and bring back up to pressure to reheat. Even though this recipe has been written for a pressure cooker, it can be prepared in a soup pot. Also note that any combination of beans can be used!