Soak the tamarind pulp in 2/3 cup boiling water for 40 minutes. Strain the tamarind into a small bowl, pressing down on the pulp to squeeze as much liquid as you can. Set the drained tamarind liquid aside.In a large frying pan or wok, heat the oil over medium heat until hot. Add the mustard seeds and cumin seeds to the pan and cook for a few minutes. Now add the urad and toor or chana dals, chilli, asafetida and curry leaves. Fry for another few minutes until the mustard seeds turn grey and begin to splutter and pop.Now add the green beans, about 3 tablespoons of the tamarind water, and salt. Reduce the heat to medium-low and cover. Cook until the beans are tender, about 5 to 7 minutes. Stir in the coconut and cook for another few minutes.Remove from heat and taste for seasoning. Serve warm alongside some fresh cooked white rice and your favorite dal dishes.