The hazelnuts add a wonderful flavor and crunch to this green-vegetable dish.
Bring a large pan of salted water to a boil. In a small skillet, toast hazelnuts over medium heat until golden brown, tossing occasionally, about 5 minutes. Transfer to a bowl; set aside.
Cook beans in boiling salted water until crisp-tender, 4 to 6 minutes; drain. Return to pan; toss with butter and half the hazelnuts. Season with salt and pepper. Transfer to a serving dish, and sprinkle with remaining hazelnuts.