Trim the ends off the beans and blanch them in a large saucepan of boiling, salted water for 3-4 minutes then tip into iced water to cool. Lift them onto a tea towel and pat thoroughly dry.

Heat the oil in a heavy-based saucepan. Add the beans and garlic and sauté over a low heat for 3 minutes, stirring frequently, or until the beans are tender and the garlic has softened and begun to colour. Stir in the butter and parsley.