Kasundi is an Indian relish or chutney, typically made in Bengal, India.
There are many different kinds; some are quite hot. Depending on the kind, Kasundi can be used as a side condiment, dipping sauces, etc.
Eggplant Kasundi (Brinjal Kasundi)
Eggplant Kasundi is made from eggplant, pepper, cumin, black sesame seed, mustard seed, curry leaves, lemon juice, tamarind paste, ghee, and chiles, simmered until thick.
Mango Kasundi (Aam Kasundi)
Mango Kasundi has mustard seed, hot red chiles, garlic, salt, and shredded mango in it. It is uncooked.
Mustard Kasundi is traditionally made in the winter. Mustard seed is ground, and put in casks of vinegar for two to three months. It turns out thinner, of course, than other Kasundis, and so is used as a dip.
Hot Tomato Kasundi (Gujarati Kasundi or Tamtar Kasundi)
Hot Tomato Kasundi is made from tomatoes, mild chiles, vinegar, ginger, garlic, oil, tumeric, cumin, palm sugar, and salt, simmered until thick.
Mango Kasundi (makes 1/2 cup)
5 oz fresh hot red chiles (seeded, stem removed)
4 cloves garlic (peeled)
1 small green mango, peeled and chopped
pinch of salt
Blend all ingredients in a blender until smooth. Put in a sealed jar and store in refrigerator; use up within two weeks.
Hiremath, Laxmi. How to Cook Fiery Chile Mustard Relish (Bengali Kasundi). San Francisco Chronicle. 24 June 1992.