For about six years I made curries that were fine. Edible, nobody complained, and they never tasted like the ones I grew up eating. I blamed the spices, then the pan, then the tomatoes.
It was the onions. It was always the onions, and the specific problem was that I was stopping about eleven minutes too early.
What the recipe says versus what happens
Nearly every written recipe says something like "fry the onions until golden brown, about five to seven minutes." I followed that for years.
Five to seven minutes gets you translucent onions with some colour on the edges. That is not the same thing. What you actually want, for most north Indian gravies, is something considerably further along — the onions collapsed, deeply coloured, the volume reduced to maybe a third of what you started with, and the whole thing turning into a paste rather than remaining as pieces.
On my stove, with a kilo of onions, that takes somewhere between twenty five and forty minutes. It is genuinely that long, and nobody writes it down because it sounds unreasonable.
Why the timing gets underwritten
I have a theory about this that I cannot prove. Recipe writers know that a step described as "forty minutes of stirring onions" will lose readers. So the time gets compressed, and the phrase "golden brown" does the work of describing a state that takes far longer to reach than the number suggests.
The other reason is that home stoves vary enormously. A wide heavy pan on a strong flame browns onions much faster than a narrow pan on a weak one, because it is about surface area and evaporation rather than heat alone.
Which means the time is never the instruction. The look is the instruction, and the look is hard to describe in text.
What you are actually waiting for
Three things happen in sequence and they are worth learning to recognise separately.
First the water comes out. The onions go translucent, the pan gets steamy, and nothing is browning yet because the surface temperature is capped by the water. This phase is unavoidable and there is no way to hurry it except with a wider pan.
Then the browning starts. Colour develops at the edges, the smell changes from sharp to sweet, and the volume drops noticeably.
Then the collapse. The pieces stop being pieces. They smear against the side of the pan instead of sliding. The colour goes from golden to a deep reddish brown. This is the stage most people never reach, and it is the one that produces the body and the sweetness that a proper gravy has.
The salt trick, which is real
Adding a pinch of salt early does help. It draws water out faster, which shortens the first phase.
What it does not do is skip anything. You still have to sit through the browning and the collapse. It maybe saves five minutes out of thirty five, which is worth having and is not the shortcut people describe it as.
What genuinely shortens it is slicing thinner and using a wider pan. A pan where the onions sit two centimetres deep will take twice as long as one where they sit in a thin layer, because evaporation is a surface phenomenon.
The burnt onion problem
The reason people stop early is that they are afraid of burning, and that fear is reasonable because burnt onion is genuinely unpleasant and unrecoverable.
What I learned, slowly, is that the danger zone is not the long middle stretch. It is the last three or four minutes, when the sugars are concentrated and the water is gone.
So the practical approach is medium heat throughout, stirring occasionally rather than constantly, and then close attention right at the end. If it starts catching, a splash of water lifts everything off the base and buys you a couple of minutes.
I keep a small bowl of water next to the stove for exactly this. It is not elegant and it has saved a lot of dinners.
What changed in the food
The difference is not subtle, which is why I am still slightly annoyed about the six years.
The gravy has body without any thickener. There is a background sweetness that I used to try to add with sugar or with more tomato, neither of which worked because it was the wrong kind of sweetness.
And the colour is right. I had assumed the deep colour of restaurant gravies came from chilli powder or from food colouring, and in some places it does. At home it comes from the onions, and once you have seen it you cannot unsee that your own version was pale.
The batch approach
Because it takes so long, I now do it once a week rather than every time.
Two kilos of onions, sliced thin, browned properly, cooled and portioned into small containers in the freezer. Each portion is enough for one gravy for four people.
It thaws in a pan in about two minutes and turns a forty minute base into a five minute one. This is the single most useful thing I do in my kitchen and I only started doing it three years ago.
The one caveat is that frozen browned onion loses a little of its texture, which does not matter in a gravy that gets blended or mashed anyway. For anything where the onion stays visible, I still do it fresh.