In large saucepan combine sugar and corn syrup, bring to boil over medium/high heat. Boil for 1 minute.
Remove from heat, stir in peanut butter and vanilla. Add cornflakes mixing until coated. Pat into a buttered 9 x 13 pan.
Evenly sprinkle marshmallows and chocolate chips over bars. Place under broiler setting on oven until marshmallows puff and brown slightly and chocolate chips are soft and spreadable.
Remove from oven, immediately spread and swirl marshmallows and chocolate chips together with a knife to evenly cover bars. Cool and cut into bars.