[1][2] It is highly pungent, and is capable of exciting the nasal passage and bringing tears to the eyes in the same way as wasabi.

[1] In modern times, Kasundi is popularly served with Bengali snacks like cutlets and chops, and deep-fried spicy treats, as it brings tartness and pungency to the flavours.

In the past, it was stored with care, served sparingly and in small quantities, and paired with hot stir-fried greens, never fish or meat.

[3][4] The practice of pairing kasundi with non-vegetarian dishes evolved in the commercial eateries, beginning with batter-fried fish.

[3][4] Kasundi has always been a revered fixture of Bengali households, its making used to be almost a religious rite, with many restrictions and rituals.

[6] Kasundi was originally used as a type of achar (literally "ritual", meaning chutney/pickle), though it was not necessarily the same sauce known today.

[1] In the past, the Bengali pickle-making season began in the month of Magh (January–February), which also is the mustard harvesting time.

Mustard was pickled before the monsoon arrived, with various indigenous fruits and greens such as coriander, pudina or amrul.

Later respected families were allowed to make kasundi following auspicious rituals while maintaining a high level or hygiene and purity.

[7] The mustard was then brought back into the house amid much ululation and lit up ghee-lamps after it has been presented to the gods.

[1] Meanwhile, water from the same pond or river in which it had been washed was boiled for a fairly long time in a freshly made earthenware pot.

[4] This is the time when the flavours developed - the distinctive pungency, the subtle tang and the spicy notes of an ideal preparation.

Then the pot was covered and sanctimoniously put in a safe place in the house to be opened on the first day of the month of Asharh (June–July).

Others used combinations of different dry and ground spices like black caraway (kalonji), fennel, wild celery (radhuni shaak) seed, ajwain, long pepper (pippali), chilli, black pepper, fenugreek (methi), clove, green and black cardamom, cumin (jeera), coriander (dhonia), nutmeg (jaiphal), mace (javitri), Java pepper (kabab chini), dried mango, dried kul etc.

[4] It also was made with a combination of fruits like mango, tamarind, indian jujube (kul) or hog plum (amda).

The more complex recipes used to have minuscule amounts of 12 masalas – haldi, dried red chilli, bay leaf, coriander, cumin, fennel, pepper, ginger, wild celery (randhuni), cinnamon, javitri or green cardamom and fennel flower (kalonji) – sometimes added with a paste of green mango as a souring agent.

[7] With phool kasundi, more chilli, turmeric, green mango and salt were added to make a grainier, bolder, fuller-bodied and spicier sauce.

[15] Green mango (kacchi kairi) is used to make chutneys, pickles, as well as different kind of curries, daal, besides aam kasundi.

Aam kasundi is enjoyed as a spread, a dip or an accompaniment with a wide range of food including sandwich, roll, burger and fritters.