To stir-fry is to sear small, thin pieces of food very quickly in a little very hot oil, keeping them in constant motion. The technique comes from China, where the wok — a round-bottomed pan that concentrates fierce heat at its base — is the classic vessel. Ingredients are cut to uniform size so they cook in minutes, added in sequence from hardest to softest, and tossed or stirred continuously so every surface meets the hot metal without burning. The result is food that is seared and smoky on the outside yet crisp and bright within, with nutrients and colour preserved by the short cooking time. A hot wok, minimal oil, and not overcrowding the pan are the three rules of success.