Fish Soup with rouille, gruyère & croutons

A favourite on the menu at the Waterside Bistro since early days. I like to keep authenticity within my dishes and so garnish with a spicy mayonnaise type sauce called rouille, toasted croutons to spread it on and finely grated Gruyère cheese, although a mature cheddar would work just as well.   Ingredients / four tarts: 500g Whole shell on …