Sauté the garlic, linguiça sausage and onion for 30 seconds over medium-high heat. Add the other vegetables and herbs, and cook for 1 minute. Add lemon juice and white wine, mahi mahi and salmon, cook for 1 minute. Add clams, mussels and prawns, chicken stock, chili flakes, salt and pepper. Cook for 2 minutes, until clams and mussels open. Finish with butter.
Serve with 2 slices of garlic bread, if you like.