In a large nonstick frying pan put the first six ingredients and stir over medium heat until the chana dal is light brown. Remove and powder in a spice grinder.
In a medium size sauce pan put the toor dal, rinse it, and add 2 cups water. Bring the water to a boil over medium heat. Cook for about one hour, adding more water as needed. The first 20 minutes I usually skim off the "guck" that comes to the surface. After about 45 minutes add the turmeric. By now you will probably need to reduce the heat to medium low. Cook until the individual dal pieces have dissolved and the mixture is smooth. Set aside.
In a large nonstick frying pan put the oil, black mustard seeds, methi, and the red and green chilies. Heat over high heat until the mustard seeds start popping. Quickly reduce heat to medium. Stir in the hing and curry leaves.
Add the mixed vegetables (carrots, green beans, tomato, potato, zucchini etc. as desired) and stir for about one minute. Add 2 cups water and cook, stirring occasionally, until the vegetables are tender.
Add the powdered spices and stir to blend.
Add the tamarind concentrate and stir to blend.
Add the cooked dal. Add salt to taste. Cook, stirring occasionally, adding water if needed, for another 5-10 minutes.
Check to make sure that no more salt or tamarind concentrate is needed.
Remove from heat and garnish with the cilantro.
If desired, you may increase the amount of vegetables in the sambar.