I have a question about Indian spices that I'm embarrassed to ask. But that's what the Internet is for.
Years ago I lived in England, and in the city where I lived there was an Indian restaurant. Actually it wasn't even a restaurant, just a husband and wife who occasionally set themselves up temporarily in a storefront somewhere, or at dinnertime in someone else's restaurant that only served lunch. They didn't advertise. People just heard they were open again and they showed up. Having eaten at one incarnation of their business, I could see why. It wasn't just better than other Indian restaurants -- it was totally different food, just amazing. I asked them what their secret was and they shrugged and said, "we grind our own spices". Ever since then, I have suspected that all normal Indian restaurants use the same Patak's or pre-ground curry powder that I can buy in the India "sweets and spices" grocery.
At one point I worked up the courage to address this theory to the owner of such a grocery. He laughed and said that there was nothing wrong with buying preground, premixed spices. He didn't even sell a spice grinder. Now, I don't believe this. When you grind anything you expose it to air and it oxidizes. Surely there is a reason to grind your spices at the last minute. Grinding your own curry powder is presumably a nuisance because it has so many ingredients. But I imagine their shelf life is quite long, so if you cook as much curry as I do then how big a deal can it be?
So here are my questions: Does it make a difference to grind your own Indian spices? How big a hassle is it? What kind of grinder do you use? And does your average Indian restaurant really not grind its own spices?
You can tell that I'm not from India. But okay, you have to start somewhere. Any clues much appreciated.