1. First, clean the bass, remove the shells and intestines from the shrimp, shred the onion, chop the leek, peel the tomato, remove the seeds and chop the green mouth.
2. Preheat a deep pan over medium heat. Pour in the olive oil, stir fry the onion, leek, tomato and garlic together for a few minutes until the vegetables are tender.
3. Add fresh fennel leaves, thyme, cinnamon leaves, shredded orange peel, stir well. Add in the mussels and stir well. Add boiling water, salt and pepper. At this time, turn to the fire, and cook for at least 3 minutes after the soup is boiled, so that the flavor of spices can be boiled out and integrated into the soup.
4. Put the fish in the boiling soup, then turn to medium heat and cook for 12-15 minutes until the fish is just cooked. At this time, the meat should be soft and opaque, but the fish still clings to the bones. Add saffron to the soup and mix well. Add in the shrimp and cook for 2 minutes.