Place beef, oil and gochujang paste in a large snap-lock bag and rub well to coat. Heat a lightly oiled char-grill pan over medium-high heat. Cook beef, in batches, if necessary, for 2-3 minutes or until browned and cooked through. Set aside on a plate loosely covered with foil.
Meanwhile, place onion and vinegar in a small bowl. Toss to coat and set aside.
Divide coleslaw and cucumber between tortillas. Top with beef and onion and drizzle with mayonnaise. Sprinkle with sesame seeds and coriander. Serve with lime wedges.
Gochujang paste is a Korean fermented red chilli paste. It is readily available at supermarkets and Asian grocers. Substitute hot chilli sauce or Sriracha sauce if unavailable.
Beef mince or stir-fry strips would also be delicious in these tacos.
Warm tortillas in microwave, char-grill/fry pan or oven.
Use any leftover beef and coleslaw to make a lunchtime salad or sandwich.