To make the crust and topping: Cut butter into the dry ingredients
in a mixer, stopping once the ingredients develop a cornmeal-like
texture. Reserve four cups of the mixture for topping. Press the
remaining mix into the bottom of a greased, 12 x 18-inch pan.
Bake at 300 degrees F until golden.
Bring butter, corn syrup, milk and brown sugar to a boil in a saucepan,
whisking constantly. Whisk at "lava" boiling stage for
five minutes. Pour over baked crust. Sprinkle remaining topping
and chocolate chips on top.
Bake at 300 degrees F until the filling
in the middle of the pan is bubbling and golden brown, about 35
to 40 minutes. Place another pan on lower rack to catch any drippings.
Cool before cutting.