Heat 1 and ½ tablespoon oil in a pan add ½ teaspoon mustard seeds, let it splutter.
Add 1 teaspoon chana dal, few curry leaves, 1 green chilli, ½ inch ginger and ¼ teaspoon hing.
Give a quick saute until dal turns golden.
Now add ½ cup finely chopped onion, salt to taste along with ¼ teaspoon turmeric powder.
Saute until onions turn transparent then add ¼ cup tomatoes.
Saute for a minute then cook covered until it turns mushy.
Then add 2 tablespoon besan flour.
Give a quick saute for a minute.
Add 2 cups water.
Mix well without any lumps.
Boil in medium flame.
Cook until thick, add 1 tablespoon coriander leaves.
Mix it well and switch off. Switch off when it is slightly runny as it thickens a bit after cooling.
Bombay Chutney is ready! Serve with idli, dosa, poori, chapathi etc.