I would butterfly open a boneless shoulder and fill it with a nice lamb sausage. Maybe something with herbs to compliment the morels. Roll it up and tie it off. Slow roast it over a bed of onions. To serve, slice it into medallions and fan it over the starch or sauce. You will probably need one or two boneless shoulders, depending on portion size and the size of the lamb. I have done this in the past with great results. This is essentially a braise. I would skip on the marinade and let the lamb speak for itself.
