The English Art of Cookery, by Richard Briggs, 1788

Take a leg of mutton that has hung up for aweek, cut the knuckle and flap off, get a quart of Oysters, blanch, beard, and wash them well, cue holes all over the mutton and stick the oysters in, tie paper over it, spit it, and roast it for two hours; then take the paper off, baste and dredge it with flour, put it into a hot dish, and garnish with horseradish, and good gravy in the dish. 

You may stew an hundred of cockles, stuff the mutton with them and roast it the same way.