1. Cut beef into 2 inches wide and 4-5 inches long strips.
2. Thoroughly wash the beef strips and squeeze out any water.
3. Place the meat in a colander and keep aside.
4. Heat oil in a frying pan.
5. Add onions and fry until light brown in colour, about 8-10 minutes.
6. Remove onions from oil and fry the whole chillies just for few seconds, otherwise they will burn.
7. Discard the oil and Grind the onions and whole chillies in a food processor to a smooth paste.
8. Place meat in a large bowl.
9. Add onion paste, ginger, salt, garam masala, yogurt, ground papaya and mustard oil.
10. Mix the mixture really well for few minutes with your hands until the meat is coated well with marinade.
11. Cover and leave to marinate at room temperature for about 3-4 hours or overnight in the refrigerator.
12. Thread meat strips onto skewers in folded layers.
13. Put skewers carefully over a gentle charcoal flame and cook until meat is brown on each side, about 5-8 minutes.
14. Transfer to a serving dish and decorate with onion ring, green chilli and coriander leaves.
15. Serve with paratha or naan and mint chutney.