A French culinary term describing dishes, classically potatoes, cooked with onions. Lyonnaise potatoes are parboiled, sliced, and fried with sliced onions in butter or oil until golden and crisp-edged, often finished with parsley. The city of Lyon’s hearty bistro cooking made the preparation famous. The term extends to other lyonnaise dishes where sweet, caramelised onions are the defining element. The slow cooking of the onions develops rich, savoury depth that complements the potatoes’ crisp exterior and fluffy interior. Served as an accompaniment to roasts and grills, lyonnaise potatoes remain a staple of French-inspired cooking worldwide.