1. Preheat a deep frying 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.
2. Add fresh fennel leaf, thyme, cinnamon leaf, 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. Discard mussels that are not open.
3. Put the fish in the boiling soup, and then turn the medium heat to boil for 12-15 minutes until the fish is just cooked. At this time, the meat should be soft, tender and opaque, but the fish is still tightly attached to the fish bone. Add saffron to the soup and mix well. Add shrimps and cook for 2 minutes.
4. After tasting the fish soup, decide whether to add more salt and spices. Divide the soup into each bowl and eat it hot.