Heat oil in a pan (on a medium heat). Add mustard seeds and cumin seeds. When they begin to pop, add the curry leaves, garlic and onions.
Saute for 3 mins and add the okra. Continue to saute for 5 mins. Stir in the red chili powder, sambar powder/ curry powder and salt.
Add the tomatoes, tamarind and ½ cup water. (If using soaked tamarind, squeeze well & strain using a strainer/filter)
Mix well and cook covered for 5 mins. Pour the rest of the water and cook till okra and sweet potatoes are fork tender. (Mine takes about 15 to 20 mins).
Stir in jaggery and coconut milk if using. Mix well and taste test to adjust salt and tamarind to your preference. It should be ideally tangy and spicy (lightly sweet if you want)
Bring to a boil and turn off the heat. Garnish Okra Curry with coriander leaves if you want and serve with brown rice, millets or eat it on its own like a meal.