Fish Stew with Aïoli

A simple version of Bouillabaisse that uses only one type of fish and is thickened by aïoli, the wonderful garlicky mayonnaise of Provence and Liguria (also called “the Italian Riviera”). Ask your fishmonger to gut and fillet the fish and to give you the head and bones for the stock, which of course can be made in advance. (Within limits you can use as many heads and bones as you like. See Fish Stock.) Serve thi