Heat oil in a pan and add mustard seeds. When they crackle, add asafoetida and curry leaves. Saute for a few seconds and add tomatoes. Mix well.
Add salt, red chili powder, cumin powder, coriander powder, and Pav Bhaji Masala. Mix well and cook until tomatoes are soft and mushy.
Add water, sugar, and finely chopped coriander, and mix well. Bring it to the boil and cook for 2-3 minutes. Add more water if needed to make the curry thin. Adjust the salt if needed and turn off the heat.
Do not add Sev at this point into the curry. Instead, serve this curry hot in an individual serving bowl. And add Sev to the top right before eating.