Thinly slice the steak into strips (about 3 inches long), and place in a large sealable plastic bag or bowl.
Whisk together the soy sauce, hoisin, pomegranate, sugar, garlic, and five spice in a bowl until well combined. Pour the marinade over the beef. Wrap tightly and place in the refrigerator overnight or for at least 4 hours.
When ready to cook, preheat oven broiler on high. Line a large baking sheet with aluminum foil and place a rack underneath the broiler.
Remove the beef from the marinade and space the pieces out on the foil-lined baking sheet. Broil for 4-6 minutes. (Keep an eye on them so they do not burn or get too dried out.)
In the meantime, bring the pomegranate juice, soy sauce, and sugar to a simmer. Stir in the cornstarch/water mixture and continue to simmer until it becomes a syrup-like consistency. Adjust the flavor if needed, with more sugar or salt.
Toss the beef in the sauce and serve. Garnish with scallions.