01Heat the oil in a kettle or a large saucepan over medium heat, and add the onions, garlic, fennel, leeks and carrots. Cook, stirring often, over medium-high heat until the mixture is wilted. Do not brown.
02Add the pepper flakes, saffron, thyme, bay leaf, fish broth, wine, crushed tomatoes, and salt and pepper to taste. Bring to a boil, then reduce the heat, and simmer for 5 minutes.
03Add the potatoes. Bring to a simmer, cover closely, and simmer for 10 minutes.
04Add the fish and the scallops. Check for seasoning. Simmer for 3 minutes; do not overcook. Add the cream, bring to a boil, remove from the heat, add the basil, and serve immediately with Parmesan croutons.