Spread the meat slices flat apart (plate if necessary). Salt, pepper and spread thinly with tomato paste. Cut the mozzarella into slices and place on top. Top with basil leaves. Roll up and pin in place. Fry the rolls in the oil all around. Deglaze with the broth and cook covered for about 15 minutes. Take the rolls out of the pan and keep them warm in aluminum foil. Reduce the brew vigorously. Stir in sour cream and season with mustard.