I think I used a base with a couple of carrots, a pepper, a tin of toms and celery in it. It would have been a ten onion batch, lightly spiced with with only one table spoon of curry powder + a few cardamom pods, a couple of star anise and a few broken pieces of cassia bark (these whole spices added after the vegs had been cooked for an hour or so and whizzed). Start by frying a couple of chopped BULBs of garlic in 500ml of oil. When browned add the onions then the rest of the vegs. Just cover with water and simmer for an hour or so. Puree with a hand blender than add the whole spices. Simmer on until the oil un-emulsifies and floats on top.
The oil from this gravy is the "spiced oil"
Think I might have put a couple of knore chicken stock cubes in too.