The French have a genius for cooking with vegetables. Even the humblest onion is transformed into something glorious in the hands of a Gallic cook. Ratatouille, one of jewels of Provençal cooking, is a fine example of that tradition. This guide is part of The New Essentials of French Cooking, the 10 definitive dishes every modern cook should master. Photographs by Francesco Tonelli for The New York Times. Videos by Alexandra Eaton and Shaw Lash.
