Heat oil in a kadai.
Add mustard seeds and fennel seeds. Let them splutter.
Add gram dal and split urad dal. Roast them to light brown stage.
Now add sliced onions and curry leaves, saute with the temper. Fry the onions to transparent stage.
Add slit green chillies. Stir well.
Put chopped tomatoes and fry them until mushy.
Put required salt.
Add turmeric powder and hing.
Mash boiled potatoes and add into the masala.
Mix well such that potatoes absorb spices.
Meanwhile make besan mix by adding some water without any lumps.
Pour this mix into the masala and stir well.
Add some water, mix with the masala.
Close the lid and cook for five mins. In between open once and stir to avoid sticking at the bottom.
Besan flour tends to increase in volume when cooked hence adjust water quantity accordingly.
When the raw flavor of the besan is removed, masala blends well.
Sprinkle some chopped coriander leaves. Poori masala is ready.
Serve hot with pooris.