In a large saucepan, combine corn syrup and sugar. Bring to a boil over medium heat; boil and stir for 1 minute. Remove from the heat; add peanut butter and mix well. Stir in the cornflakes and peanuts. Press into a greased 15x10x1-in. pan.
In a microwave, melt chocolate chips, peanut butter and shortening; pour over bars and quickly spread evenly. Refrigerate for 2-3 hours or until set before cutting.