Gundruk

gundruk ko saag

A summer of greens, kept until March.

What it is

Gundruk is leafy greens, usually mustard or radish tops, wilted, packed tight into a jar or an earthenware pot and left to sour in their own juice for a week or two, then pulled out and dried in the sun until brittle. The result keeps for a year and looks like dark khaki straw. It tastes nothing like the fresh leaf it came from: sour, deeply savoury, slightly funky, closer to sauerkraut than to spinach.

Where it comes from

It belongs to the Nepali hills, where the growing season is short and the winter long, and where a household that did not preserve its greens simply went without. The same logic produced sauerkraut in Germany and kimchi in Korea. Nepal's version is drier, because drying was the only storage a hill house could rely on.

What it's called

Gundruk (Nepali). The radish-root version of the same ferment is sinki, which is a different thing in the pot.

In the kitchen

Rinse it, squeeze it dry and chop it. Then dry-roast it in a pan for thirty seconds before any liquid goes near it, which wakes the sourness and takes off a dusty note that otherwise runs straight into the broth. From there it goes into a thin sour jhol with soybeans and potato, or gets fried crisp in mustard oil and tossed as a salad. Never add tamarind or lemon to a gundruk dish; the sourness is meant to come from the ferment alone.

What we know about the claims

It is a fermented vegetable, so the usual claims about gut bacteria follow it around. Sun-drying kills most of what was living in it, so treat gundruk as a preserved vegetable with real vitamin C and iron, not a probiotic. It is also high in salt from the ferment, so season the finished dish late.

Choosing and buying

This is the one Zone VI item reliably stocked in Britain. Nepalese Centre carries a 200g pack for under four pounds, and Nepal Foods Online and My Spice Shop sell smaller sizes. In the US, any Himalayan or Nepali grocer online. Dried mustard greens from a Chinese grocer are the nearest substitute at a push, though they are milder.