Adjust the oven rack to the lower middle position. Preheat oven to 350F. Place a large sheet of foil under the rack in case the pie bubbles over.
Lightly flour a clean work surface. Unroll pie crusts and stack on top of each other. Use a rolling pin to combine crusts into a 17 x 12-inch rectangle. Roll the pastry around a rolling pin and then unroll over a rimmed 15 x 10-inch sheet pan; fit to the pan, fold under the edges and crimp. Refrigerate while preparing filling.
In a large mixing bowl whisk together the brown sugar, KARO syrup, melted butter and vanilla until combined. Add the beaten egg and whisk again until smooth. Fold in the peanuts with a spatula until all nuts are evenly coated.
Remove the crust from the refrigerator and sprinkle with 3/4 cup of the chocolate chips across the entire surface. Gently and slowly pour the peanut filling mixture evenly over the chocolate chips. Gently move the filling around with a fork to fill the corners, and make it level. Bake for 25-30 minutes or until the topping is bubbling across the entire surface and the crust is lightly browned.
Remove from the oven and let the pie rest for 5 minutes or until it no longer bubbles. Scatter the top with the remaining chocolate chips.
Cool completely in the pan then slice and serve.