Heat olive oil and butter in a large heavy soup pot or Dutch oven over medium heat. Add onions and sauté for a few minutes until translucent.
Add the garlic and cook one minute until fragrant.
Deglaze the pan by adding the white Vermouth. Cook for a few minutes to allow the alcohol to cook off.
Add all the bay leaves, salt, Italian seasoning, black pepper, and red pepper flakes. Stir to mix with onions and garlic and then add chopped tomatoes and tomato paste. Stir.
Add parsley. Stir to incorporate and then add fish stock. Stir, cover, and turn to low. Allow to simmer for 10 minutes.
After 10 minutes, add halibut and allow to cook for 3 minutes. Now add shrimp and scallops. Allow to cook for a few more minutes until fish, shrimp, and scallops are cooked through.
Ladle into individual serving bowls and top with additional fresh parsley. Serve with crusty toasted bread or baguette for dipping. Enjoy!