Line two baking sheets with parchment paper or silicone baking mats.

In a large saucepan, combine the sugar, corn syrup and peanut butter over medium heat.

Stir often until the peanut butter mixture comes to a boil. Continue boiling for 2 minutes, stirring frequently, then remove from heat and stir in the vanilla and cornflakes.

Use a cookie scoop to portion out the cornflake mixture in 2-3 tablespoons sized cookies onto the prepared baking mats.

Let set for 1-2 hours before storing or serving.