Gochujang, a fermented chili paste essential in Korean cooking, gives these sandwiches lots of pungent, spicy flavor. If you can't find it, substitute with a mix of 1/3 cup white miso, 3 tbsp. Sriracha chili sauce, 1 tbsp. unseasoned rice vinegar, and 1 tsp. regular (Hungarian) paprika.
1 cup mirin (sweet sake)
2/3 cup reduced-sodium soy sauce
1/4 cup toasted sesame oil
2 teaspoons sugar
2 garlic cloves, crushed
1 flank steak (about 1 1/4 lbs.)
SLAW AND SANDWICHES
3 tablespoons gochujang (Korean chili paste)
2 tablespoons toasted sesame oil
2 tablespoons reduced-sodium soy sauce
1 tablespoon sugar
2 green onions, chopped
4 cups shredded napa cabbage (from 1 medium head)
6 tablespoons mayonnaise
6 crusty sandwich rolls, such as Mexican torta rolls or bolillos
2 tablespoons cilantro leaves
How to Make It
Marinate beef: Combine mirin, soy sauce, 1/3 cup water, the oil, sugar, and garlic in a bowl and stir until sugar dissolves. Pour mixture into a 1-gal. resealable plastic bag. Add steak and marinate, chilled, at least overnight and up to 2 days.
Heat a grill to medium (350° to 450°). Make slaw: In a large bowl, whisk chili paste, oil, soy sauce, sugar, and green onions together until sugar dissolves. Add cabbage and toss to mix well.
Grill beef (discard marinade), turning once, 6 to 15 minutes total (depending on thickness) for medium-rare. Transfer to a cutting board and let rest 10 minutes.
Slice beef across the grain. Spread 1 tbsp. mayonnaise inside each roll. Fill rolls with meat and slaw, and tuck a few cilantro leaves into each.