Lyonnaise Onions

• 1.5 kg Brown onions
• 75 g Unsalted butter
• Salt

Peel the onions, cut in half and slice as thinly as possible. Melt the butter in a heavy-based saucepan; when foaming, add the onions and cook for 2½–3 hours over a very low heat until all the juice has evaporated. The onions will caramelise and take on a deep, golden brown colour. Season to taste with salt and freshly ground pepper. If not using immediately, spread the onions on a tray and ref