Lettuce and Mint Soup

• 2 oz / 60 g butter
• 4 oz / 110

Melt the butter in a heavy saucepan. When it foams, add the onions and potatoes, and turn them until well coated. Sprinkle with salt and pepper. Cover, and sweat on a gentle heat for 10 minutes. Add the chopped lettuce leaves and stock. Boil until just tender, but do not overcook or the lettuce will lose its colour and flavour. Make a purée in a blender or food processor (after cooling slightly