Wash asparagus under cold running water. Snap off lower end of each stalk with your fingers. Let the stalk break where it wants to, this will leave only the tender portion of the stalk. Young tender asparagus can be cooked in a steamer for 5-7 minutes, the more mature stalks for 7-10 minutes. Do not over cook asparagus, it will lose flavor and nutrients if over cooked. At the same time, place the hazelnuts and butter in a small heavy skillet. Heat until the butter melts and mix thoroughly. Remove from heat and stir in vinegar. Season with salt and pepper to taste. Pour hazelnut butter over hot asparagus. Serve at once.