Heat the oil in a large frying pan (skillet) over medium heat.
Add all the ingredients, except the lemon juice, mango and salt.
Stir-fry for a few seconds.
Remove from the heat and allow to cool.
When cool, transfer the mixture to a blender or food processor.
Add mango and lemon juice, and season with salt.
Then process, adding a little water if necessary to make a smooth paste.
Transfer the paste to a bowl.
Heat the oil for the tempering in a frying pan over medium heat.
Add the chana dal.
Stir-fry for about 1-2 minutes, or until light golden.
Add the dried red chillies, and curry leaves and stir-fry for a few seconds.
Mix well with the chutney.
This chutney should be eaten immediately.