1. Remove the tough green stalks from the leeks, leaving the white end. Halve it, rinse it well, and slice it thinly.
2. Cut the fronds off the ends of the fennel bulb (reserve for garnish if you like). Trim the end, cut the hard, V-shaped core out of the center bottom, then slice thinly.
3. Slice the garlic cloves thinly.
4. Heat oil in a large, shallow pan over medium heat. Add leek and fennel and sauté until softened, about 4 minutes. Add the garlic cloves and cook until fragrant, 1 additional minute.
5. Add the drained tomatoes and wine (or pastis) and let cook for about 2 minutes, until reduced slightly. Add the saffron threads, bay leaf, broth and salt and pepper to taste. Simmer on medium-low heat 10 minutes, allowing the saffron to infuse the broth with flavor.
6. Add the cod pieces, cover and cook gently 3 minutes.
7. Add the prawns and mussels, cover the pan and simmer an additional 3 to 4 minutes, until the cod is cooked through, the prawns are pink, and the mussels open. Scallops and lobster tails should appear opaque. (Note: If you use frozen mussels, they have been par-cooked and pasteurized, so even unopened ones are perfectly safe to eat.)
8. Remove the bay leaf, check seasoning and serve piping hot with garlic-rubbed toasts. Enjoy!