Pommes soufflées are a variety of French fried potato. Slices of potato are fried twice, once at 150 °C (300 °F) and a second time after being cooled, at 190 °C (375 °F). The potato slices puff up into little balloons during the second frying and turn golden brown. Pommes soufflées were, according to a famous legend, discovered by chance on 24 August 1837, when Queen Marie-Amélie and other notables were delayed in their arrival for a meal at the Pavillon Henri IV in Yvelines after inaugurating the first passenger steam-powered railway in France. The chef Collinet, reputedly also the inventor of sauce béarnaise, removed the already frying potatoes from the oil and observed them expand when, after the royal party had arrived, they were returned to the oil. This story has been disputed on a number of grounds.