Unfortunately, I was unable to find a good cooking class in Pondi. There were a couple of French bakery and pastry classes, which, me being French, did not interest me.
I did however have a fascinating meeting with the lady who wrote the ultimate book on Pondicherry cooking. I can give you references for her book if you're interested. I can also tell you how to get in touch with her. But she does not give classes.
Plenty of classes on offer in South Goa, but I preferred to go to a restaurant whose cooking I really liked and got 2,5 hrs of training for 1,500 Rs. The advantage of doing that is you're on your own and you actually get to cook a lot. The "cooking classes" I was told about consisted mostly of a chef cooking and a bunch of people paying good money to watch him, which is not what I'm looking for. Most restaurants don't have the equipment necessary for 10 people to cook the same dish at the same time. You want to collect as much info as you can on the actual content of the class beforehand.
I realize this is not a lot of help. But my experience from this past trip is that it's no use trying to make reservations in advance from Europe. Much better to look up the places that advertise their classes on site - they do that with posters and flyers on trees and lampposts in the most touristic places, and with ads in local papers / websites. Or better still, just find a restaurant you like and talk the chef into some private training.
Good luck and bon appetit !