In a large saucepan, combine corn syrup and powdered sugar over medium heat. Stir constantly for 3–5 minutes until the mixture begins to bubble. Remove from heat once boiling.

Stir in peanut butter and vanilla extract into the hot corn syrup mixture until blended smooth, taking about 1–2 minutes.

Gently fold in Rice Krispies cereal until all pieces are evenly coated, taking care not to crush the cereal. This should take around 2–3 minutes.

Drop scoops of the mixture onto a silicone mat or waxed paper. Let cool for about 10 minutes.

Once cool enough to handle, dampen hands and roll the mixture into golf ball-sized balls.

Store the rolled balls in an airtight container at room temperature for 30 minutes to set fully.