Mustard oil: how to use it in your kitchen

What is mustard oil?

Mustard oil is pressed from mustard seeds, usually the brown or black varieties. Cold-pressed oil, known in South Asia as kachi ghani, is golden to amber and has that sharp, nose-tingling pungency you also get from English mustard or horseradish. In Bengali, Bihari and Punjabi homes it is the default cooking fat, used where other kitchens would reach for sunflower or olive oil, and many families have cooked with nothing else for generations.

At Tukwila you'll find several mustard oils, including Radhuni, Ifad, Alibaba, Heera and TRS, in bottles from 250 ml up to 1 litre. They all live in our oils and essences section.

Read the label first

This catches a lot of people out: in the EU, some bottles of mustard oil carry the words "for external use only" (in German, "nur zur äußerlichen Anwendung"). That wording comes from EU rules on edible oils. For cooking, always choose a bottle that is clearly labelled as edible or cooking oil. It takes ten seconds to check, both when you buy and before you cook, and it removes any doubt.

How to heat mustard oil

Raw mustard oil is fierce, so many cooks temper it before adding anything else:

1. Pour the oil into a dry frying pan or karahi over a medium-high heat.
2. Wait until it just starts to smoke and the colour turns a shade paler, usually after 1–2 minutes.
3. Take the pan off the heat for about 30 seconds, then add your spices.

This mellows the sharpness without scorching the seeds. For dishes where you want the raw mustard bite, such as bhorta or jhal muri, the oil goes in unheated – but only ever use an oil labelled for food.

Five classic ways to use it

1. Bengali fried fish

For machh bhaja, rub 500 g of fish pieces (rohu and hilsa are favourites) with 1 tsp turmeric and 1 tsp salt and leave for 10 minutes. Heat 4–5 tbsp mustard oil until it just smokes, then fry the fish over a medium heat for 3–4 minutes on each side. Don't throw away the frying oil: a spoonful over hot rice with a little salt and a green chilli is a treat in its own right.

2. Bhorta and jhal muri

For aloo bhorta, mash 3 boiled potatoes with a finely chopped onion, 1–2 green chillies, salt and 1 tbsp raw mustard oil. For jhal muri, toss two handfuls of puffed rice with chanachur, onion, cucumber, fresh coriander and 1 tsp mustard oil – the street snack of Kolkata and Dhaka, ready in two minutes.

3. Pickling

Mustard oil is the traditional base for mango, lime and chilli pickle. A simple mango achar for a 500 ml jar: cut 500 g green mango into chunks, mix with 1 tbsp salt and 1 tsp turmeric, and let it dry out for 1–2 days in the sun or somewhere warm. Stir in 2 tbsp coarsely ground mustard seeds, 1 tsp fenugreek, 1 tsp nigella seeds and 2 tsp chilli powder. Heat 150 ml mustard oil until it smokes, let it cool completely and pour it over until the mango is covered. Leave the jar to mature for about a week and always use a clean, dry spoon.

4. Tempering with panch phoron

For Bengali dal or labra (mixed vegetables), heat 2 tbsp mustard oil, add 1 tsp panch phoron and 2 dried red chillies and wait until the seeds crackle. Pour this tadka over finished dal, or use it as the starting point for your vegetables.

5. Sarson ka saag and Punjabi tadka

In Punjab, mustard oil goes into the tadka for sarson ka saag: heat 2 tbsp oil, fry garlic, ginger and onion until golden and stir it into the mustard greens. If fresh mustard leaves are hard to find, tinned sarson ka saag finished with this tadka is a very decent shortcut.

Kasundi: mustard, Bengali style

If you love the flavour of mustard, try kasundi, a punchy Bengali mustard sauce. It is a brilliant dip for pakoras, fish cakes or simply cucumber with a pinch of salt, and it sits alongside mustard oil in any Bengali kitchen. You'll find it with our pickles.

Beyond the kitchen

In many South Asian households mustard oil is also used for massage or for oiling hair in winter. That is a cosmetic tradition, and it is exactly what the bottles labelled "for external use" are meant for. Keep your cooking bottle and your body-care bottle apart, and label them clearly so nobody mixes them up.

Storage

• Keep mustard oil somewhere dark and cool with the cap tightly closed, not right next to the hob.
• Use an opened bottle within a few months, while it still smells fresh and sharp.
• If the oil smells rancid or musty rather than pungent, stop using it for cooking.
• Leftover frying oil can be cooled, poured into a clean jar and used within a few days.

Common mistakes

Oil that is too cold leaves spices flat; oil that is too hot burns cumin and nigella in seconds, so always let it cool briefly after it smokes. If the flavour feels too strong at first, there is no shame in mixing mustard oil half and half with a neutral oil. You'll get used to it quickly – and before long you may find that fish fried in anything else tastes oddly bland.