If you are using homemade tamarind pulp, just dissolve that in water. But if you are using tamarind fruit, soak the fruit in water for 15 mins and then squeeze the pulp and juice out of it and strain the water.
Take a mortar and pestle or a small grinder and add pepper, red chilli, garlic in it and crush it roughly.
Heat ghee in a sauce pan. Add in mustard, asafoetida, curry leaves and saute for a min.
Now add in half of the crushed masala and saute for a min.
Pour in tamarind juice and water.
Now add the remaining crushed masala and mix well.
Season with salt.
Bring this to a boil and once it reaches boil, throw a handful of coriander leaves and switch off the flame.