1. In a large kettle or soup pot, bring the water and 3 tablespoons of salt to a bubbling boil over high heat. Drop the beans in by the handful. Return the water to a boil, reduce the heat to moderate and boil the beans uncovered for 10 to 15 minutes, or until they are just tender. Do not overcook them.
2. Immediately drain them in a large sieve or colander. If the beans are to be served at once, melt 2 tablespoons of butter in a 2- to 3-quart saucepan and toss the beans with the butter for a minute or two, season them with salt and pepper, then transfer them to a serving dish.
3. If the beans are to be served later, refresh them after they have drained by quickly plunging the sieve or colander into a large pot of cold water and letting it remain there for 2 or 3 minutes.
3. Drain the beans thoroughly, place them in a bowl, cover and set aside-in the refrigerator if they are to wait for long. If you plan to serve them hot, reheat them in 2 tablespoons of hot butter, season them and let them warm through over moderate heat.
