Ratatouille is proof that the best summer cooks the cheapest. It comes from Provence, in the south of France, and started as a humble country dish of summer vegetables slowly stewed in olive oil. Today we also know it in its more striking version - thinly sliced rounds of vegetables arranged in a spiral over a tomato base, baked in the oven.

The ingredients are simple and you have them all on hand at this time of year: aubergine, courgette, tomatoes, onion and garlic, plus good olive oil and a sprig of rosemary. For a dish 24-26 centimetres across you need half an onion, two cloves of garlic, 300 grams of puréed tomatoes, one courgette, three tomatoes and one aubergine.

The method is easier than it looks. First sauté the onion and garlic in olive oil until soft, then add salt, the puréed tomatoes and the rosemary and cook for about ten minutes. Spread that mixture over the bottom of the dish. Slice the vegetables into thin rounds and lay them alternately in a spiral over the tomato base, drizzle with olive oil, salt and pepper, and bake at 180 degrees for about 50 minutes.

The secret isn't in any expensive ingredient, but in two details. First - cut the vegetables evenly, or part will burn while another stays raw. Second - use meaty tomatoes, with less water, so the flavour doesn't get watered down. And most important: let the dish rest a little before you serve it. As with most good things, here too patience makes a difference you can't buy.