Combine toor dal, mung dal, and lentils, wash thoroughly, and then soak for two hours or longer.
Prepare paste while dal is soaking. In a blender, combine garlic, ginger, tomatoes, cumin seeds, garam masala, coriander, cayenne pepper, fenugreek seeds, fennel seeds, cilantro, mint leaves, tamarind paste, and water. Grind to a smooth paste. Set aside.
After dals have soaked for two hours or longer, drain off the water. Combine dals, 4 cups of water, salt, turmeric, squash, and eggplant. Bring to a boil, reduce heat, and simmer for 25-30 minutes, until the dals and vegetables are very soft. Stir to smooth consistency.
In a large fry pan, heat oil on medium-high heat. Add onion and saute until golden brown. Add the paste mixture that you set aside and stir. Add dals and vegetables and stir to coat everything and mix the spices. Add 1/2 cup of water or more to desired consistency. Mixture should appear thick like stew. Bring to a boil and then reduce heat to low, cover and simmer for 10 minutes to allow the flavors to meld.
Serve over a bed of hot rice.