1In small bowl, mix all tangy sambhar powder ingredients. Heat 6-inch skillet over medium-high heat. Place mixture in skillet; cook 1 to 2 minutes, stirring constantly, until seeds crackle, spices turn 1 shade darker and the mixture has a nutty, pungent aroma. Transfer to a bowl; cool 8 to 10 minutes.
2Place 3 tablespoons mixture in spice grinder. Grind until mixture resembles texture of finely ground pepper. Repeat with remaining mixture. Store in airtight jar at room temperature for up to 1 month; beyond that, it will start to lose its full flavor. Makes about 1 cup spice blend; use 1 teaspoon for this recipe.
3To make curry, in wok or deep 12-inch skillet, heat oil and mustard seed over medium-high heat. Once seed begins to pop, cover wok and wait until popping stops. Add asafetida and 2 tablespoons split peas; cook and stir about 1 minute or until peas are golden brown. Add sweet potato, karhi leaves, salt and 1 teaspoon of the tangy sambhar powder; cook and stir 1 to 2 minutes.
4Stir in water. Heat to boiling; reduce heat. Cover and simmer 5 to 7 minutes or until sweet potato is tender.