Soak tamarind in ¼ cup hot water. Let it soften and later squeeze to extract some juice. Filter the tamarind juice to a small bowl and set aside.
On a low to medium heat, dry roast peanuts until golden & aromatic,
Then add sesame seeds and coconut. Fry until they begin to smell good. Transfer and cool them.
In the same pan, heat 1 tbsp oil and saute onions until golden.
Add ginger garlic paste & saute until the raw smell disappears. Cool this as well.
Blend together all the roasted ingredients and onions with ¼ cup water. Make a thick slightly coarse paste.
Rinse the green chilies and wipe them dry. Make an slit lengthwise and deseed the seeds.
Heat oil 1 tablespoon oil in the same pan and fry chilies for 2 to 3 minutes until they blister. Set aside.
Heat another teaspoon oil in the same pan. Add mustard seeds & cumin. When they pop, add curry leaves and fry until the leaves turn crisp.
Turn down the heat and add the onion peanut and coconut paste.
Pour water. Stir and make a thin gravy. Incorporate the paste with the water to make a gravy before the water turns hot.
Next add chili powder, tamarind juice, garam masala and turmeric.
Stir and simmer for 5 to 8 minutes until slightly thick. Add fried chilies and simmer on a low heat until they wilt. Taste test and adjust salt and tamarind if required.
Salan turns thick further upon cooling so turn off when it is slightly runny but yet thick.
Serve mirchi ka salan with any biryani.