Make a paste by pureeing the spinach, cilantro and mint in a food processor, with a tbsp or two of water. (don't go overboard on the mint otherwise the whole paste tastes bitter)
Heat the oil on medium and throw in the cardamom pods, cloves and cinnamon stick. After 1 minute add the onion and saute till golden-brown.Then put in the green chillies, chopped garlic and ginger and cook for another minute.Stir in the beef, red chilli powder, ground cumin, garam masala, ground black pepper, salt and cook on medium-high heat for 10 mins, stirring often.
Add half of the yogurt and mix well till incorporated and cook for another 2 mins.Put in all of the green paste, mix well, and simmer for 10 mins.Stir in the rest of the yogurt, cooking the whole thing for a further 5 mins. Taste for salt.