Kasundi

Bengali mustard sauce

The queen of Bengali pickles — fierce, fermented, and once made only by ritual.

What it is

Kasundi is a fermented mustard relish, and the fresh article bears little relation to the mild jarred “kasundi” sometimes sold abroad. It is sharp and pungent enough to prickle the nose and bring tears, closer in effect to wasabi than to table mustard. At its simplest it is mustard seeds, salt, chilli and water, ground and left to ferment; often green mango or a run of spices join it.

Where it comes from

It is Bengali through and through — West Bengal and Bangladesh. Historically its making was a ceremonial, caste-bound affair begun on the spring day of Akshaya Tritiya, when the early-summer weather was judged right for fermentation: warm enough to work, not so hot as to spoil. Well made and sealed, it was said to keep for years — the “queen of pickles.”

What it's called

Kasundi · kasundi shorshe. Variants include aam kasundi (with green mango) and the coarser phool kasundi.

In the kitchen

Kasundi is a condiment, not a cooking spice — served alongside fried snacks, cutlets and chops, spooned over steamed greens and vegetables, used as a dip or a dressing. Its job is to add a fierce mustard tang; a little sits beside the food rather than being cooked into it.

What we know about the claims

As a fermented food it carries the general gut-flora interest that ferments attract, and mustard its own compounds — but it is eaten in spoonfuls as a relish, so read it as flavour, not function. Its heat can be genuinely strong; newcomers should start small.

Choosing and buying

Jarred kasundi is in most UK and US South Asian grocers, though the commercial versions are milder and smoother than a home ferment. For the real thing, seek a small-batch producer or make it — ground mustard, salt, chilli, water, left to ferment and sealed under a film of mustard oil.