Note: The chickpeas need to be pre-cooked or canned ones may be used.
Pre-heat oven to 350 degrees. In a large, heavy skillet or pot, brown the onions in moderately hot oil along with the cumin seeds and mustard seeds. Add the potato pieces (peeling is optional), and stir to coat each piece with the spices. Now add the remaining spices and continue to stir for several minutes.
Thin the tomato paste with about 2/3 cup of water. Stir into the pot. Add vegetables, one at a time, cooking for a minute or so between each addition, and put in the cooked chickpeas last. If your pot is not oven proof, transfer mixture to one that is. Cover with a lid or seal with foil and bake for about 45 minutes, checking after the first 20 minutes.
The consistency should be rather thick, but add liquid if necessary to prevent burning. Stir occasionally to prevent sticking. Serve over rice or with Indian bread.