Dahl refers to pulses that have been split in two, and to a creamy stew commonly made from these pulses across the Indian subcontinent and in the West. In Britain at least, the pulse used is nearly always the lentil, which is widely available and cheap. Lentils are one of humanity's oldest foodstuffs, and they were eaten widely in the Middle Ages across Europe, but suffered from a decline in popularity in recent centuries as they came to be seen as inferior to high-calorie foodstuffs that required more complex processing.
In Britain, it didn't help that during the period of the empire they came to be seen as the food of backwards people who lived under British rule in India. In the early twentieth century, when nutritional science was significantly less developed than today but racial prejudice significantly more developed, Indian pupils were being taught that dahl produces "paralysis of the legs" (I think they meant this metaphorically rather than literally; rice, meanwhile, they dismissed as "not very nourishing").
Ironically, it was only when the empire crumbled and immigrants started coming to the British Isles from India, Bangladesh and Pakistan that the love of lentils was reintroduced to Britain, this time in the form of dahl. While the transmission of recipes and food from former colonies to former colonizers is common across the world, I'm not aware of any country in which the process has reached quite the same level as in Britain. Chicken tikka masala, a meat curry, has been found to be the most popular dish in British restaurants, and one of our Conservative-led government's few economic interventions has been to establish a school to train more chefs in South Asian cookery, so precious are their skills to the national stomach.
Dahl lags far behind meat curries in the level of appreciation it receives in the UK, which is a shame. Lentils are an extremely healthy food, with some varieties containing the same protein content as meat, but with virtually zero fat. If you're a vegetarian - which I decidedly am not - then dahl deserves to be a staple dish, as most of its bulk consists of the protein-rich lentils. If you eat it with rice, it forms a complete protein, meaning at least in terms of protein it is a substitute for meat. It's plentiful in iron, too.
Dahl, once cooked, is a thick stew, almost like a thick porridge. It's quite homogenous in appearance, but the trick is to season it with other ingredients like ginger, garlic, chillies and shallots. As the dahl tends to envelop all the other ingredients, you usually never know what you're going to get in each mouthful. You can serve the below recipe with rice and flatbread, or - as I like to do - serve it with fish or meat, meaning that the dahl itself becomes the side.
To make dahl, you're going to need the following. This recipe will make a serving for one hungry person, or two with sides:
- Lentils - any type will do, but I generally use split red lentils. You need about 100g per person, which is about what you get in a small bowl
- Two cloves of garlic, crushed
- Two chillies, chopped finely
- Two shallots, chopped
- A bunch of coriander (cilantro to you Yanks), chopped
- A piece of ginger, about 4cm long, but chopped finely
- Cumin seeds
- Mustard seeds
- A tablespoon or so of turmeric
- A few tablespoons of cooking oil, preferably groundnut
Most of the cooking process with dahl is a process of boiling the lentils until they break down and become a stew, and letting them absorb the other ingredients. Start by washing the lentils repeatedly in a small bowl, pouring the dirty water away and repeating the process until the water runs nearly clear; otherwise, the dahl will end up with a slightly scummy taste.
Then put the lentils into a fairly deep but not too wide pan, and cover them until they're about an inch underwater. Don't worry too much about getting this right, because you can add more water later. Bring the water to a boil, then reduce to a simmer and whack in the garlic, chillies, ginger and turmeric. The turmeric has a slightly earthy flavour, but its main purpose is to impart a pleasing yellow colour which will characterize the entire dish once its done.
Now it's a waiting game. You simmer the pan for about an hour and a half, adding more water if it's boiling away, until you can no longer distinguish individual lentils but instead have a thick stew. Taste it as you go along to make sure the consistency is right, and add more seasonings if you want. When it's at the desired consistency, heat a small frying pan over a high heat, put the oil in, and then quickly fry the shallots, cumin seeds and mustard seeds - this cooks the shallots and releases a more intense flavour from the seeds. You'll know it's done when the shallots are browning and the mustard seeds are starting to pop (try to dodge them). Quickly mix the contents of the frying pan into the larger, dahl-containing pan, stir and then serve. The coriander ought to be scattered over the dahl once it's on the plates, as if it's heated too much it becomes icky.
I often serve dahl with plain white fish, which you can mix in or serve on top. Enjoy!
My main source for this was dating a Bangladeshi. For the quote about paralysis of the legs, see Nick Cullather, 'The Foreign Policy of the Calorie', American Historical Review 112, 2 (2007).