Finely dice the ham. Heat oil in a pan. Fry the ham until crisp. Pluck the mozzarella into pieces. Chop parmesan cheese into shavings.
Clean, wash and shake the salad dry, cut in half lengthwise and cut into strips. Peel onions and cut into fine strips. For the dressing, mix sour cream, mayonnaise, lemon juice and half parmesan.
Season to taste with salt, pepper and sugar.
Mix salad, mozzarella and ham, arrange and sprinkle with dressing. Sprinkle with the remaining Parmesan cheese.