Heat oil in a large frying pan over medium-high heat. Add onions. Sauté, stirring occasionally, for 2-3 minutes or until browned.
Add ginger, garlic and green chilies. Sauté, stirring, for about 1 minute or until fragrant.Reduce heat to medium-low.
Add ground turmeric and red chili powder. Sauté, stirring, for a minute or until aromatic. Add tomatoes. Sauté, stirring occasionally, for 2-3 minutes or until the tomatoes break down and turn mushy.
Add lamb (or mutton). Cook, stirring with a wooden spoon to break up mince, for about 8-10 minutes or until browned. Season with salt.
Add garam masala and coriander (cilantro) leaves. Stir to combine. Cook, stirring occasionally, for another 3 minutes.
Garnish with more coriander (cilantro) leaves if you like.