Preheat the oven to 180 degrees. Cut off the meat, score the fat. Rub with mustard powder, pepper and salt. Heat the frying fat in the frying pan. Quickly sear the meat with the fat side down. There should be a brown crust on all sides.
Place the meat, fat side up, in a roasting pan. Roast for 25-30 min. per 500g weight to get it “medium”. Let stand for 15 min before carving.
For the pudding, sift flour and salt into a suitable bowl, stir through and add egg and water. Mix to form a paste. Heat milk and add, beating until smooth. Pour drippings or melted butter into 12 small baking cups. Heat in the oven at 210 °C for 5 minutes. Divide the dough evenly into the ramekins, bake for about 10-15 min, until they have risen.