Cook sweet potatoes either in a pressure cooker or a saucepan.
Once cooked, peel off the skin of the sweet potatoes and mash them. Keep aside.
Put the roasted peanuts in a food processor and grind them to a coarse powder. Keep aside.
In a kadai warm a tablespoon of oil and add urad dal. Once it turns light brown, add cumin seeds and mustard seeds.
Once the seeds splutter, add the chopped onion. Fry for a minute.
Add chilli powder and salt and fry for another minute.
Once the onion turns translucent (not burned) add the sweet potato and mix well. Simmer.
Make sure the onion and other ingredients are well blended with the sweet potato.
Now add the coarsely ground peanut powder and mix well.
Switch off the flame and serve with hot tea/coffee.