Score the flank steaks; make light diagonal slashes in diamond shapes on each side of meat. Place flank steaks in large baking dish (I used a 9" X 13" glass baking dish).
In large bowl, combine soy sauce, honey and red wine vinegar until honey dissolves. Add garlic powder and ginger, mix, then add oil and scallion, mix well. Pour marinade over meat, flip steaks to cover completely. Cover tightly with plastic wrap and refrigerate 6 - 12 hours, or overnight, turning occasionally.
At least one hour before serving, make the creamy lime sauce; whisk together all ingredients and cover and chill.
Bring steaks to room temperature for about half an hour, then heat grill to medium. Remove flank steaks from marinade and grill about 6 minutes a side for medium doneness. To serve, slice thinly on the diagonal, with creamy lime sauce on the side.
Depending on appetites, this serves 8 - 10.
I used low-sodium soy sauce.
I'm pretty sure my Chicago friend got this recipe from Southern Living, over 20 years ago. I couldn't find it online to provide a credit/link.