Hi Secret Santa , basically I stumbled across this technique by accident, and was experimenting with 3 things, 1) high heat during cooking, 2) adding water to thin the base during cooking. 3) longer evaporation of the base. This technique I use with bhuna is basically using high heat, with the addition of water to stop the tom puree and the base going brown during cooking. I noticed years ago that if the tom puree and base goes to dark it ruins the curry. I now believe this can be stopped if the base is very very watery, or you add a little water at the right time during cooking. Its essential to evaporate off the water, and aim to end with a dry curry. I had some good results with this technique, and believe its very similar to the way the chef at my local cooks bhuna. He adds a little ghee which is also good for high heat cooking. Using 2 pans was also a technique he used for my curry, presumably it improves heat distribution, and evaporation. He then tipped the contents of both pans into 1 silver TA container. it was the best bhuna he ever made me. I still remember it well ! ;D