This is place that has an open plan kitchen and hes always happy to chat to me, I had the Bengali tikka jalfrezi which I have already posted the recipe for on this site.
His English is not fantastic so take the following with a pinch of salt:
They dont use oil skimmed off the top of the curry gravy
They cook the base the day before, and always use it the following day (this I am highly dubious about, he did have a new pot on the go when I was there which he showed me in addition to the rather full one on the stove so it may be true but I cant imagine he would use all the pot in 1 night)
He didn't scoop off gravy from my curry and put it back in the pot (this may of course have been because I was watching him cook)
I asked about the ingredients and cooking the base, he said veg oil and ghee (showed me a massive tub of veg ghee), ginger, garlic, onions, peppers, carrot and spice mixture, think he said coriander stalks also. He said it takes 3-4 hours to cook the base, he also said they use ghee when precooking meat but not in cooking the final curry, he also reminisced about the good old days when he would pour melted ghee over the finished curries?
