Recipe serves 3-4. Increase quantities to serve more, and add different vegetables as desired for variation.
- Olive oil
- 1 onion
- 1 clove garlic, or to taste
- 1 eggplant (aubergine)
- 1 green, red, yellow or a combination, bell pepper
- 2 zucchini (courgettes)
- 6 medium tomatoes, ripe (juicy), peeled and seeded
- salt and pepper to taste
- Herbes de Provence to taste, (optional), or
- 1 small bunch basil, chiffonéd (optional)
- Put a large casserole on the stove on medium heat.
- When the casserole is hot, add enough olive oil to just cover the bottom.
- Cut the zucchini and eggplant  . Add to the casserole.
- Sauté the slices until light brown; remove from pan and set aside temporarily.
- Chop the onions and garlic.
- Cut the green pepper into strips or dice, as preferred.
- Add some additional oil if needed, and cook the onions and peppers slowly for about 10 minutes until tender but not brown. Stir in the garlic.
- Peel and seed the tomatoes. Dice them or cut them into quarters, add to the casserole. Add some salt to bring out their juices. Cover and lower the heat.
- Five minutes later, check to see if the tomatoes have made enough juice to almost cover the vegetables - if so, perfect. If not, add water as needed (not too much).
- Add salt, pepper and Herbes de Provence to taste. In general, 1 tsp of salt, 1/2 tsp of pepper and 1 tbsp of the herbs will suffice.
- Add the zucchini and eggplant back and blend gently with the tomato-onion-pepper mixture. Cover the casserole and let simmer on low heat until the vegetables are tender but still intact, 10 to 20 minutes, or to taste.
- Remove the lid, raise the heat a little and cook uncovered for another 15 minutes, basting frequently until the liquids have mostly evaporated, leaving a small amount of juice and olive oil.
- N.B. It is important that each of the vegetables retain its own shape and character. Most authorities agree that ratatouille should not be a mush. Avoid overcooking. Sautéing the eggplant and courgettes initially helps retain their shape and improves their flavour, but is optional. Of course if you personally prefer a more homogeneous dish, it may be cooked for 45 minutes to 1 hour, but this is unusual.
- When ratatouille is used as a filling for savoury crêpes or to fill an omelette, the pieces are sometimes cut smaller.
- While most recipes do not brown the onions, if you like them browned, brown them. Food traditions have always been subject to individual interpretation.
- Unnecessary moisture can also be reduced by straining the liquid into a pan, reducing it over heat, then returning the reduced liquid to the casserole.