Ratatouille is usually served as a side dish, but may also be served as a meal on its own (accompanied by pasta, rice or bread). Tomatoes are a key ingredient, with garlic, onions, courgette, aubergine, bell peppers, marjoram and basil, or bay leaf and thyme, or a mix of green herbs like herbes de Provence. Ratatouille can be eaten for dinner, but is also used in breakfast and lunch settings. There is much debate on how to make a traditional ratatouille. One method is simply to sauté all of the vegetables together. Some cooks, including Julia Child, insist on a layering approach, where the aubergine and the courgette are sautéed separately, while the tomatoes, onion, garlic and bell peppers are made into a sauce. The ratatouille is then layered in a casserole – aubergine, courgette, tomato/pepper mixture – then baked in an oven. A third method, favored by Joël Robuchon, is similar to the previous; however, the ingredients are not baked in an oven but rather recombined in a large pot and simmered. When ratatouille is used as a filling for savory crêpes or to fill an omelette, the pieces are sometimes cut smaller than in the illustration. Also, unnecessary moisture is reduced by straining the liquid with a colander into a bowl, reducing it in a hot pan, then adding one or two tablespoons of reduced liquid back into the vegetables.