For the beef lung roast with black walnuts, remove the meat from the refrigerator in time and let it come to room temperature.
Salt, rub with ground pepper, allspice and mustard and tie into shape with kitchen twine. Heat olive oil in a roasting pan and sear fillet together with shallots and garlic.
Place the meat on slices of brown bread and roast in a preheated oven at 190 °C for approx. 15 minutes. Keep basting with drippings and turning. Take out roaster, remove bread slices and let fillet rest in aluminum foil for 10 minutes in turned-off oven with open oven door.
In roasting pan, cream butter with rosemary sprigs. Add black walnuts as well as balsamic vinegar and boil down until the sauce caramelizes slightly. Pour in some more vegetable stock if necessary.
Remove kitchen twine from fillet and roll in ham chip powder. Cut into 8 slices, arrange on warmed plates and top with the nut sauce. Remove the garlic from the skin and serve with the beef lung roast with black walnuts, as well as the shallots.