Combine first 4 ingredients in 2-quart microwave mixing bowl. Microwave on HIGH for 8 minutes, stirring after 4 minutes. Add butter. Microwave on HIGH 2 minutes. Brittle should not get too brown. Stir in vanilla and soda until light and foamy. Spread on buttered baking sheet as thinly as possible. Cool. Break into pieces. Soak mixing bowl in warm sudsy water immediately for easier clean-up.

Note: exact cooking times may vary depending on your microwave wattage.