I don't know what you could add to it now, but could I pass this recipe on to you?.
It makes a really delicious curry. Though when I make it I use tinned tomatoes, add extra garlic, a tin of 'blitzed' chickpeas, and a tbsp of garam masala. A word of caution - if you don't like it too hot, add less chilli powder.
You can use any meat for it, doesn't have to be lamb. Good luck.
http://www.bbcgoodfoo...curry?pager.offset=40