Step 1: Awaken the Aromatics
In a large, heavy-bottomed pot or Dutch oven, heat the ¼ cup of olive oil over medium heat. Once it shimmers, add the sliced leeks and fennel. Sauté, stirring occasionally, for about 8-10 minutes, until they have softened considerably and become translucent. You are not looking for browning here; you want to gently coax out their natural sweetness. Add the minced garlic and red pepper flakes and cook for another minute until fragrant.

Step 2: Bloom the Saffron and Deglaze
Add the 2 tablespoons of tomato paste to the pot. Stir it into the vegetables and let it cook for about 2 minutes. This step caramelizes the paste, deepening its flavor and removing any “tinny” taste. Now, pour in the 1 cup of dry white wine to deglaze the pot. Use a wooden spoon to scrape up any flavorful browned bits from the bottom. Let the wine simmer and reduce by about half, which should take 3-4 minutes. As it reduces, crumble the ½ teaspoon of saffron threads into the pot. The warm liquid will help the saffron “bloom,” releasing its vibrant color and aroma.

Step 3: Build the Broth
Pour in the 6 cups of fish stock and the 28-ounce can of diced tomatoes (with their juices). Add the 1 teaspoon of dried oregano. Stir everything together, bring the mixture to a gentle simmer, then reduce the heat to low. Cover the pot and let the broth simmer for at least 20-30 minutes. This is a critical step that allows all the flavors to meld together into a cohesive, delicious base. Don’t rush it! Taste the broth and season with salt and freshly ground black pepper. Be mindful that the seafood will add its own saltiness later.

Step 4: Cook the Seafood in Stages
The secret to perfectly cooked seafood is not to overcook it. This is achieved by adding the different types of seafood in stages, according to their cooking times.

• First, the Fish: Increase the heat to a medium simmer. Gently add the chunks of firm white fish to the broth. Let them cook for about 3-4 minutes.

• Next, Clams and Scallops: Add the scrubbed clams and the optional scallops to the pot. Cover and cook for another 3-4 minutes. You will start to hear the clams popping open.

• Finally, Mussels and Shrimp: Add the mussels and shrimp. Stir gently to submerge them in the broth. Cover the pot again and cook for a final 3-5 minutes, or until the shrimp are pink and opaque and all the mussels and clams have opened.

Step 5: Final Touches and Serving
Turn off the heat. Carefully inspect the soup and discard any mussels or clams that did not open during the cooking process. Gently stir in most of the chopped fresh parsley, reserving some for garnish. Ladle the soup generously into large, shallow bowls, making sure to distribute the different types of seafood evenly. Garnish each bowl with a sprinkle of the remaining fresh parsley, a few delicate fennel fronds, and serve immediately with thick slices of crusty bread and lemon wedges on the side.