Bombay chutney (besan chutney) is a curry-like dish made using chickpea flour and spices. It is a great side dish for poori, dosa, idli, chapati, or roti. Here is how to make it.
Make a lump-free slurry. Whisk besan with ½ cup of water first, until completely smooth. Only then add the remaining 2 cups of water. Adding all the water at once is the number one reason people end up with lumpy chutney.
Temper the spices. Heat oil in a pan over medium-high heat. Add mustard seeds, cumin seeds, hing, and curry leaves. Let them crackle for 5-6 seconds until fragrant.
Cook the onion and chili. Add onions and green chilies. Cook until the onion turns soft and translucent, not brown.
Add tomato and ginger. Stir in tomatoes and ginger. Cook for two to three minutes until the tomato softens.
Season the base. Add turmeric, chili powder, garam masala, and salt. Cook for about a minute so the spices toast slightly rather than taste raw.
Pour in the slurry and simmer. Lower the heat to medium-low before adding the besan slurry. This step matters, since pouring flour batter into a very hot pan makes it bubble and spit. Stir often and cook for 12 to 15 minutes, until the mixture thickens slightly and the raw, flour-like smell disappears completely.
Finish and serve. Check for salt and add more if needed. Stir in cilantro. Squeeze some lime juice on top and serve hot.