Cut onions into rings, salami into strips and sauté both in oil until golden, add the finely grated apple, sugar and vinegar. Pour beer, fill with warm beef broth and make meanwhile until the onions are soft. Cut the rolls in half lengthwise and fry them in a frying pan in clarified butter – on both sides – sprinkle with cheese and parsley and bring to the table on the spot in the hot soup.
By the way, did you know that clarified butter is obtained by extracting water, milk protein and lactose from butter?