Chocolate chex Caramel Crunch

I found this recipe on the back of the chocolate chex box.

8 cups chocolate chex
3/4 cup brown sugar (packed)
6 tablespoons of butter
3 tablespoons light corn syrup
1/4 tsp baking soda
1/4 cup vanilla baking chips to drizzle over finished mix (I never add this part)
1. Microwave brown sugar, butter, and corn syrup uncovered stirring every minute until melted and smooth.
2. Pour butter mixture over cereal and stir.
3. Microwave for 3 more minutes stirring every minute.
4. Spread to cool. May need to break into pieces.