Prepare the fennel: Cut off the stalks. You can use the fronds later in the week. (Think salads, sauces, mixed with goat cheese, sprinkled over fruit...) Then halve the bulb and remove the core. Slice the bulb thin. You may want to quarter the bulb for smaller slices.
Place a large stock pot over medium-high heat. Add 2 tablespoon oil to the pot. Sauté the fennel and onions for 5 minutes; then add the garlic and tomato paste.
Sauté one more minute. Then add the tarragon, thyme, saffron, red pepper, bay, salt and black pepper to taste. Mix well. Pour in the wine, stock, and tomatoes. Bring the stew to a boil. Lower the heat, cover, and simmer for at least 30 minutes.
Meanwhile, cut the fish into 1-inch cubes and toss the fish and shrimp in flour. Rinse and check all mollusks for freshness. They should all be completely closed. If they are open, squeeze them shut. If they don’t instantly close up again, THROW THEM OUT. Any open or cracked mollusk should not go in the cioppino.
Once the stew has simmered for 30+ minutes, add the mollusks. Stir and allow them to cook for 3-5 minutes until they are mostly opened. Next add the fish and shrimp. Stir well and simmer another 3-5 minutes. The broth should thicken and all the mollusks should open wide.
Remove the thyme sprigs, bay leaf, and any unopened mollusks. Garnish the cioppino with parsley and lemon wedges. Then serve with lots of warm crusty sourdough bread or parmesan toast.