In a large sauce pan add the peanut butter, sugar and brown sugar and corn syrup. Cook over medium heat stirring occasionally until smooth. Remove from heat and add the chocolate chips, peanuts and cornflakes. Mix well quickly before it begins to harden, making sure everything is evenly coated.
Press the mixture in a 9x13 inch baking dish and smooth out using a spatula or a knife. Allow it to cool completely before cutting into bars.