1. Soak the tamarind in hot water for 10 minutes and take out the pulp (you should be able to get 2 cups of tamarind water from this).
2. In a microwave safe bowl, add toor dal in 1 cup of water and microwave it for 3 minutes.
3. In a pan, heat oil, fry mustard seeds, urad dal, garlic, fenugreek seeds, cumin seeds, green chillies, curry leaves, toor dal, sambar powder and ground onion for 3 minutes.
4. Add chopped onion, hing, salt, tomato and stir for few minutes.
5. Add chopped brussel sprouts, 1 cup tamarind concentrate and mix for 3 minutes.
6. Add the remaning tamarind, 1 cup water, grated coconut and mix gently.
7 Stir in the gram flour, 1 cup water and cook covered for 7 minutes.
8. Serve the curry with white rice, or chapati garnished with chopped cilantro.