Line a baking sheet with parchment paper and set aside.
Add the cornflakes to a large mixing bowl.
3 cups cornflakes cereal
In a medium saucepan, combine the sugar, corn syrup, peanut butter, and vanilla extract.
½ cup light corn syrup, ½ cup sugar, ½ cup peanut butter, 1 teaspoon vanilla extract
Cook over medium heat, stirring frequently, until the mixture starts to bubble.
Continue cooking for a few minutes until the sugar is fully dissolved and the mixture is smooth.
Remove from heat and pour the peanut butter mixture over the cornflakes.
Gently fold the mixture together until all cornflakes are evenly coated.
Drop spoonfuls onto the prepared baking sheet and sprinkle with Christmas sprinkles if using.
Christmas sprinkles
Chill in the refrigerator for 1 hour, or until set.