Season the halibut fillets with a pinch of salt. Set aside.

In a large pot, heat olive oil over medium heat. Add chopped onion, fennel, carrot, celery, and minced garlic. Cook until the veggies are soft, about 3 minutes.

Mix in the basil, parsley, and tomato paste. Cook, stirring occasionally, for about 2 minutes until the paste darkens.

Pour in the white wine, increase the heat to medium-high, stir, and let it evaporate, cooking for about 1 minute.

Add diced tomatoes, vegetable broth, thyme, bay leaf, and hot sauce. Bring to a simmer and cook for about 10 minutes. Season with the remaining salt and black pepper.

Add the shrimp, mussels, clams, and halibut pieces to the pot. When the soup begins to boil, skim off any foam. Let it simmer for 5 minutes, or until all the seafood is cooked through.

Garnish with fresh parsley and basil to taste. Serve hot with sourdough bread on the side.