I made an oil-free base gravy years ago, to try and produce some low cal, low-fat curries. It worked up to a point but you still had to start the curry with some oil to get anything that tasted remotely like BIR. So all in all, I felt it was not really to my taste. I'd be interested to hear how you get on though.
Here is my recipe. It is basically just about a Taz base without oil and I notice it was done in 2014:
No Oil Base (enough for 9 curries)
Ingredients:
6 large onions, approximately 1kg peeled weight, roughly chopped
12 cloves of garlic, peeled and chopped, approximately 2 oz in weight
2 inch x 1 inch piece of ginger, chopped, approximately 1 oz in weight
1 average sized red pepper, roughly chopped
2/3 tbsp salt
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