Cut the beef lung roast into strips and fry in hot oil for about 1 minute so that the meat is still pink inside. Cut the lemongrass stalk diagonally, the chili peppers as well as the shallots into fine rings. Finely chop the ginger and garlic. Now mix the lemongrass, chili, shallots, ginger and garlic together with fish sauce, lime juice, sesame oil as well as salt to a marinade. Pour over the seared beef and marinate with it. Arrange the beef on plates or in bowls and garnish with cilantro.