Heat a little oil in a pan and add the chopped potato, brinjal, tomato, and capsicum. Saute for a few minutes.
Add salt to taste, mix well, cover the pan, and cook on low heat for about 10 minutes, stirring occasionally, until the vegetables are tender.
Once the vegetables are cooked, mash them well with a spatula.
In the same pan, heat a little more oil for the tadka. Add mustard seeds, cumin seeds, asafoetida, and curry leaves. Let them splutter.
Add the finely chopped onion and saute until it turns light brown.
Stir in the crushed garlic and green chillies. Saute for a couple of minutes until the raw smell of garlic disappears.
Add a pinch of turmeric powder and mix well.
Add the mashed leftover vegetables to the pan and mix thoroughly with the tadka.
Add red chilli powder and the crushed roasted peanuts. Garnish with chopped coriander leaves and mix well.
Cook for another 2-3 minutes. Serve hot.