For sugo di pomodoro, mash tomatoes with a potato masher in a large bowl, then add bay leaf and set aside. Heat oil in a large saucepan over medium heat and sauté onion and garlic until soft and translucent (6-10 minutes). Add tomato and bay leaf, reduce heat to low and simmer, stirring occasionally, until a thick rich sauce forms (1-1¼ hours). Season to taste.
Heat oil in a saucepan over high heat. Add mussels, garlic and chilli, and stir occasionally until mussels begin to open (2-3 minutes). Add wine, parsley and tomato sauce, cover with a tight-fitting lid and cook until mussels open fully (2-3 minutes). Scatter mussels with extra parsley and serve with toasted sourdough.
