Cut steak or lamb into cubes. Heat oil and fry the mustard seeds until they burst. Add the fenugreek, garlic, ginger and onion. Fry until onions are golden. Add turmeric and fry for 1 minute. Add the coriander, cumin and chilli. Stir well.
Add salt and vinegar, and fry until the liquid evaporates. Sprinkle in the garam masala powder and mix well. Add the meat and turn until it is coated.
Add the cubed potatoes and cover. Cook for another 20-30 minutes or until the potatoes are cooked.
Sprinkle with finely chopped coriander, green chilli and garam masala powder