Line a baking sheet with foil. Butter the foil, and set aside. In a heavy 8-inch skillet, combine nuts, sugar, and butter. Cook over medium heat, stirring constantly, for 9 minutes or till sugar melts and turns a rich brown color. Watch out for splatters. Remove from heat. Immediately stir in vanilla. Spread mixture onto the baking sheet. Cool completely. Break into small clusters. Store tightly covered. Makes 2 3/4 cups. From Better Homes and Gardens.