In food processor, pureacute;e onion, garlic, ginger, 2 red chilli and 1 green chilli with a bit of water to get it going. Process to fine paste.
In a non-stick saucepan or wok, melt butter and heat oil till hot.
Add mustard seeds, stirring, they should crackle. If they dont crackle, your oil is not hot enough. Stir for about 20 seconds.
Add asafoetida powder and stir for 10 seconds.
Add cumin seeds and stir for 30 seconds.
Add curry leaves, they will pop and crackle and my spit oil. Stir for another 15-30 seconds, being careful not to burn them.
Add pureacute;e of onions etc., cook for 5 mins over medium heat.
Add ground coriander,cumin,garam masala, turmeric, salt,cardamom.corn flour, stir and cook for another 3 mins.
Add meat, stir until well mixed and coated with mixture, about 2 mins or so.
Add tomatoes, bring to simmer.
Add spinach mix and up to about 1 cup of water.
Bring to a rapid simmer, stir for about 5 mins.
Reduce to slow simmer and cook for about 1 hour or until lamb is tender. Stir frequently. Add more water as needed and to adjust consistency.
Remove from heat. Add yogurt and mix in well.