I love how tender the mutton meat cooked this way turns out. It literally gets to an almost 'falling off the bone' tenderness, very enjoyable with pita bread or parathas or even baked potatoes.
Boil the mutton meat with 1 grated tomato and 1 grated onion, 1 tsp. salt, 1 tsp. pepper, half tsp. garlic paste and 1/2 tsp. ginger paste....until almost completely tender. Make sure you use just enough water such that it is not in excess. If a little water remains after boiling, it's ok, drain it from the meat and set it aside to be used later.
In a separate pan, add the oil, followed by the sliced onions. Fry until golden, then add the garlic and ginger paste. Stir-fry for a minute, then add the boiled mutton pieces and fry them in the oil. Add the green chillies, yoghurt, the cumin, turmeric, chilli powder and black pepper. Keep the heat on low and keep stirring everything together until the yoghurt is no longer visible.
Now add the extra water if you want it to have a bit of gravy/moisture (you can add just a bit of regular water if none remained after boiling the meat). Let this simmer for a few minutes until the masala is thick, then squeeze the lemon and sprinkle the garam masala and chopped coriander. Taste and adjust salt and pepper. Cover and keep on low heat for about 5 minutes then switch off and serve.
You can garnish with sliced onions and chopped coriander or mint. You can even garnish with veggies or french fries.