In a large saucepan, bring the corn syrup and sugar to a boil over medium heat, stirring constantly. Boil just until the sugar is completely dissolved and the mixture is smooth.
Stir in the peanut butter until fully combined. The mixture should be smooth and creamy.
Remove the pan from the heat, and stir in the vanilla extract. Fold in the cornflakes until they're evenly coated (be careful not to crush the cornflakes while mixing).
Using a tablespoon, drop the mixture onto a sheet of waxed paper. Let the chews cool completely at room temperature until they're set.
