Using the food processor, put diced cooked beef in the bowl, a pinch of mace, some freshly ground black pepper, softened butter in equal proportion to the meat, or less butter if you prefer, and a dash of port or Madeira, as well as 2-3 tablespoons of gravy if there is any left. Blend until smooth, spoon into a bowl, and pour clarified butter over the top, which will seal it until required. Refrigerate.