Tian Provençale with Rosemary & Olives

The tian is a type of gratin from Provence which owes its name to the glazed earthenware dish in which it is cooked. Instead of layering the vegetables on top of each other and cooking them in eggs and cream, as in a gratin dauphinois, they are packed tightly, moistened with olive oil and set almost upright in the dish. Courgettes, tomatoes, aubergines, onions and garlic are the most popular vegetables used and, like its cousin ratatouille, the tian can be served hot, w