Dum Aloo

Why are the potatoes pricked before they go into the gravy?

A boiled potato has a sealed, waxy surface that liquid runs off rather than enters. Six or seven holes give the spiced gravy a route inside, and after a quarter of an hour on a low flame the potato tastes of that gravy the whole way through instead of being a bland lump in a good sauce. The frying that follows firms the surface so those holes stay open and the potato holds its shape during the long simmer. Leave out either step and what you get is potatoes in curry.

Why does the curd split, and what prevents it?

Curd splits when its proteins hit direct heat too quickly and tighten into visible grains. Three habits prevent it. Whisk the curd until it is entirely smooth before it goes near the stove, take the pan off the flame while you pour it in, and stir without stopping for the first couple of minutes as the heat comes back. A tablespoon of gram flour beaten into the curd gives extra insurance by holding the water in suspension. Full fat curd is much more forgiving than low fat here. The same principle governs Punjabi kadhi, where yoghurt is the entire dish rather than part of it.

What separates Kashmiri dum aloo from the Punjabi version?

They are barely the same recipe. The Kashmiri Pandit style contains no onion, no garlic and no tomato whatsoever; its flavour comes from fennel powder, dry ginger powder, asafoetida and a large quantity of Kashmiri chilli used for colour rather than heat, all in a thin curd gravy. The Punjabi version starts with browned onion and tomato, finishes thicker, frequently takes cream, and tastes much closer to a restaurant gravy of the shahi paneer family. Bengali dum aloo is a third thing again, lighter and slightly sweet.

Do the potatoes have to be deep fried?

No, although it does change the result. Deep frying blisters the surface and firms it so the potato survives the simmer whole. Shallow frying in two tablespoons of oil, turning them every minute or so, gets most of the way there for a fraction of the fat. An air fryer on a high setting for around twelve minutes is the cleanest option of the three, though the surface stays drier and takes up a little less gravy. What will not work is dropping boiled potatoes straight into the pan, because they break apart and thicken the gravy with starch.

What is the dum step actually doing?

Dum means cooking under a tight lid on a very low flame so the food sits in trapped steam and its own aroma. Here it is not cooking anything further, since both the potatoes and the gravy are already done. It is the absorption stage, and fifteen minutes is roughly what a pricked potato needs. A heavy pan holds that low heat far more evenly than a thin one, and a lid weighted with a bowl of water seals better than a loose one.

Storing it, and reheating it without ruining the gravy

Three days in the fridge, and it is better on the second day because absorption carries on in the cold. Reheat gently with a splash of water, since a curd gravy boiled hard on reheating will separate even when it survived the first cooking intact. Freezing is not worth attempting; the potatoes turn grainy and watery. Serve it with jeera rice or plain roti rather than anything else rich. If you want to work through this whole family of gravies methodically, the culinary nutrition course takes them apart technique by technique.