How to make it
In a re-sealable plastic bag, place steak and Black Pepper Sauce. Close bag and shake until the sauce is evenly distributed. Refrigerate and allow to marinate for at least 2 hours.
Heat a grill or grill pan on high heat. Grill steak for 4-5 minutes on each side. Transfer meat onto a cutting board, rest for 5-7 minutes. Slice into portions.
To assemble the Torta, cut bolilos in half and spread refried beans on each side.
Place bok choy, nappa cabbage, tomato, avocado, steak on to the bun and top with Sriracha Mayo.