Butterfly the loin by slicing along the side. Work towards the center of the loin and stop when you are about one inch from the edge.
Prepare an all cotton trussing string by making a slip knot with a large loop.
Spoon stuffing into the center of the butterflied pork loin.
Roll the loin around the stuffing and place the loop of twine around one end. Pull this tight.
Make a loop with the end of the string on the top of the loop.
Fold the loop over the end of the pork loin and pull it down about 1 1/2 inches and gently tighten. Repeat this step until the loin is trussed and tie off the end.
You will have to keep the stuffing in place as you truss the loin and after it is trussed and tied stand the loin on its end and gently press in more stuffing.