Chop bacon slices into smaller pieces to form squares. Fry bacon until crispy and then add mushrooms, onion and garlic. Simmer until mushrooms and onions are soft in texture. Drain grease from pan and cool stuffing mixture down in the refrigerator. When stuffing is cooled, add gorgonzola by crumbling it and incorporating it into the mixture. Pile stuffing on one side of the “open” roast, roll it up to bring the roast back together and use string or food bands to secure it.
Heat oven to 400 degrees. Sear the roast in a hot pan or on the grill, then cover it with foil and finish it in the oven until the internal temperature reads 146F for medium rare. Let it stand a few minutes before carving.