Microwave Crunchy Caramel Corn

In large microwave-safe bowl, combine popcorn, cereal and nuts. In 4-cup measuring cup, combine butter, brown sugar, corn syrup and salt. Microwave on HIGH for 1-1/2 minutes; stir. Microwave on HIGH for 45 seconds to 2 minutes until mixture comes to a rolling boil. Stir in vanilla and baking soda. Mixture will become foamy. Pour over popcorn mix; toss to coat. Spread half of mix evenly in 12x8" dish. Microwave on HIGH for 2-3 minutes or until popcorn is evenly coated and glazed, stirring every minute. Spread on foil to cool. Popcorn will become crisp as it cools. Using same dish, repeat with remaining popcorn. Allow mixture to dry for 2 hours. Store in tightly covered container.