I have just got back from Zaffron after a very interesting and enlightening Madras cooking lesson. I was only there for an hour so didn't get a chance to cover anywhere near as much as I would have liked, but I did get to cook a Madras from scratch including the base in about 30 mins. I'm going back in a couple of weeks for a longer stint so hopefully I can cover more areas then.
Interestingly, there was no Garam Masala or Restaurant Spice Mix. He had 5 big tubs containing Turmeric, Salt, Hot Chilli Powder, Ground Cumin and ground Coriander.
As the main restaurant batch of base was already made, the chef made up a small individual batch to show me how to do it. This was priceless as far as cooking from home goes, and the finished result was simply sublime.
So for the base he got a metal frying pan and added a lot of vegetable oil. I'm guessing 6 to 7 tablespoons worth. To thins he added two chefs spoons of finely chopped onion and green pepper (about an 80/20 split). After a couple of minutes he added in two green finger chillies which had been split lengthways. When this was was just starting to think about browning, he added in about 2 tablespoons of finely chopped carrot and continued to fry. He added a couple of teaspoons of ginger garlic paste (60% garlic 40% ginger) which they make themselves by blending the chopped ingredients with water. Next was a ladle of blended tinned plum tomatoes which were cooked for 2 - 3 minutes. then he added 1 tsp chilli powder, 1/2 tsp ground cumin, 1.5 tsp ground coriander, 1 tsp turmeric and 1 tsp salt. Once this had cooked for about 5 minutes he added about 2 tablespoons of plain yoghurt. He added water (half a metal serving bowl) and simmered for a few minutes. He then poured it into a blender to be finely blended. this whole process only took about 20 minutes. The finished base sauce didn't taste that nice. it was quite spicy and very salty but this was apparently normal as it gets thinned out with water at the curry cooking stage.