Add the 4 cups of Cornflakes to a medium bowl and set aside.
In a medium saucepan combine the sugar and the syrup. Over medium-high heat, while stirring, bring the mixture to a boil. Remove for the heat and add the peanut butter and the vanilla and stir until blended.
Pour the mixture over the Cornflakes and stir until all the Cornflakes are coated.
Drop by round tablespoons (I used a medium cookie scoop) onto wax paper.