Sprinkle the cabbage leaves with 1/2 tsp salt and let stand about 15 minutes until they wilt. Squeeze out any moisture, then rinse and dry the leaves. Chop the cabbage. In a bowl combine the cabbage, beef, scallions, garlic, soy sauce, sesame seeds, sesame oil, pepper and 1/4 tsp salt and mix thoroughly. To make each dumpling, place 1 1/2 teaspoonful filling in the center of a wrapper using two spoons. Fold the wonton wrapper in half to form a semi-circle (if using round wrappers) or a triangle (if using square wrappers). Seal the edges by moistening them with a little water and pinching them. You may freeze the dumplings at this point on a cookie sheet or continue to use them by frying, steaming or in a soup.
To Fry: Heat oil in a wok or frying pan to 360 degrees. Fry about 10 at a time for 3 minutes or until golden.
To Steam: Arrange on lightly oiled plate, but do not let them touch each other. Pour about 2 inches of boiling water into a wok, set the plates in the steamer and set the steamer in the wok. Cover the steamer and cook over medium heat for 20 minutes.
Skillet Method: In a 12" skillet heat 2 tablespoons of oil until hot. Fill the skillet with mandu, making sure that they do not touch. Cook until the bottoms brown; about 1 minute. Add 1/3 cup water or beef broth to the skillet and cover and cood for about 10 minutes.
Serve Yakimandu with Dipping sauce.