Sambar and vadas are a traditional pair in South Indian cuisine. There are as many variations of sambar as there are households in India, but they generally fall into one of three major types: tamarind, tamarind and dal, and buttermilk. I prefer the thick tamarind and dal sambar, both for taste and $$$ savings.
Many spices used in Indian cuisine are used as much for medicinal purposes as taste. According to Ayurvedic principles, ginger and turmeric are digestive aids and are often added to a pot of boiling legumes.
Mysore vadas are pretty different from the amai vadas I made a while back. Instead of the typical ground lentils, mysore vadas are made from a mixture of rice, all-purpose white, and semolina flours. For my personal variation, I replaced the all-purpose white flour with whole wheat pastry flour with a touch of baking soda.
The stiff batter was easily shaped into rounds ahead of time. With lentil vadas, this preliminary step is nigh impossible, as the lentil batter will spread out over time. In practice though, I discovered this really didn't save much time at all.
The following spices were fried in oil and then ground into a paste with a bit of water: fenugreek seeds, chana dal, coriander seeds, cumin seeds, white poppy seeds, and black peppercorns. A hallmark of South Indian cuisine, and part of what differentiates it from North Indian cuisine, is the use of roasted/fried dals as spices.
Fried spices must be cooled sufficiently before adding them to an electric grinder with plastic parts. To quickly do this, spread them out thinly in a metal pan and place the sheet over a cool surface.
After the masala paste (diluted first in some more water) is added to the cooked dal, the following spices were fried and added whole: hing, curry leaves, and mustard seeds.
This process is known as "tempering", "chaunk", and "tarka" in various regions of India.
Sweet Potato Sambar and Mysore Vadas, served with Tamarind Chutney
If you're curious about this dish, as well as South Indian cuisine in general, check out Dakshin: Vegetarian Cuisine from South India.