1. Combine the soy sauce, black rice vinegar, sesame oil, ginger, garlic and black pepper in a small bowl (do not use metal).
2. Stab your beef with a fork.
3. Add the beef to the marinade. Make sure it's evenly coated!
4. Cover with foil and leave in the fridge to marinate, from 1/2 hour to 3 hours, depending on how strong you like the flavours.
5. When ready to cook, preheat the oven to 180 degrees Celsius.
6. Slice the pita bread into half carefully and grill it until toasted. Remove and put on a plate.
7. Remove your beef from the fridge and pour whatever remaining marinade into a frying pan.
8. Heat until it starts to bubble, then add your beef.
9. (Depending on how you like your beef to be cooked, and also the cooking time here will change.).
10. Cook for about 2 minutes on each side, turning beef with a pair of tongs.
11. Put a leaf of lettuce on your pita bread, followed by tomato, then the beef and another leaf of lettuce.
12. Devour. Warning: it's gonna get messy.
13. OAMC INSTRUCTIONS:.
14. To freeze: place marinade ingredients and meat in a zip top bag. Freeze.
15. To serve: Thaw and cook as desired.