Preheat the oven to 350°F. Line a 13x9 inch metal pan with foil and spray foil with cooking spray.
Combine the flour, sugar and salt in large bowl or in the bowl of a food processor. Cut in butter with pastry blender or pulse the processor until mixture forms fine crumbs. Add 1 egg and process until moist.
Press firmly onto bottom of prepared pan and bake for 25 minutes.
Meanwhile, In a large mixing bowl, beat together the condensed milk, remaining egg and maple flavoring; stir in nuts.
Sprinkle the chocolate chips evenly over prepared crust, then pour the condensed milk/nut mixture over the chips.
Return to oven and bake for an additional 25 minutes or until golden.
Let cool completely, then lift from the pan and cut into bars. For easier slicing, I recommend chilling the bars before cutting.