I've read that restaurants use an onion gravy which, I imagine, is similar to your basic curry sauce.?

Question

I can't believe that a restaurant would use an enormous blender for the sauce. How do they get it so smooth?

Answer 1

Yes you're right. All restaurants use a stock sauce. And, yes, they DO use a blender but not the familiar kitchen type.
A curry chef would use a huge hand held blender with a rotating blade on the end. You can buy smaller versions for home use but they are about a foot long and pretty weedy. The industrial version is about 3 feet long and quite heavy.
In a restaurant they boil down the onions with garlic, ginger and spices and puree it all right there in the pan. Then they fry and reduce down the rather sloppy sauce in oil to make each dish.

Answer 2

any basic gravy or curry sauce as u say it is simply just onion paste fried a bit initially to get rid of the raw smell & then ginger garlic paste is added to it. after frying a while u can add either finely chopped tomatoes or pureed ones along with some salt, turmeric & chilli powder. your basic sauce is ready to be used. in a restaurant they do have huge grinders & also hand held blenders.

Answer 3

Normally in Indian cooking, the onions are fried till brown making it crispy. While continuing the cooking, the crispy onions partly disintegrate into the curry. Ordinarily in Indian cooking there is nothing like onion sauce as a separate food item but onions are used in almost all curry preparations this way.