Grease a small baking sheet; set aside. In a microwave-safe 4-cup glass measure, combine sugar and corn syrup. Microwave mixture, uncovered, in a 900- to 1200-watt microwave oven on 100% power (high) for 5 minutes, stirring twice.Advertisement
Stir in nuts and butter. Microwave mixture, uncovered, on 100% power (high) for 1 to 2 minutes more or just until mixture turns golden (mixture continues to cook and becomes more golden when removed from the microwave).
Stir in vanilla and baking soda. Immediately pour mixture onto prepared baking sheet. Use two forks to lift and pull candy into a thin sheet as it cools (this helps make the brittle crisp).
Cool brittle completely. Break into irregular pieces. Makes about 1/2 pound.
Layer pieces between waxed paper in an airtight container; cover. Store at room temperature for up to 1 week.