COOK corn syrup and sugar together in a large pan over medium heat, stirring to dissolve sugar. Bring mixture to a boil. (Or in a 1 quart microwave-safe container; microwave on high (100%) for 2 to 2-1/2 minutes until syrup boils). Remove from heat.
STIR in baking soda and vanilla until blended thoroughly. Stir in 1 cup chocolate chips until completely melted and smooth. Add 1 cup M&M candies and cereal and stir to coat completely.
POUR into greased 13 x 9-inch pan; pat into place.
TOP with remaining M&M candies.
COOL and cut into squares. Store in tightly covered container for up to 2 days.