Wash the beans and remove the ends and strings, if there are any. Leave them whole or cut them in diagonal strips.
Drop the beans into a large pot of boiling water and boil them gently until just done, allowing about 5 - 10 minutes, depending on the size and age of the beans. Taste one to see if it is done; it should still be very crunchy.
Drain the beans and rinse them thoroughly in cold water to stop the cooking.
Reheat them in lots of butter, salt, and pepper just before serving.