The right way to prepare and cook onions

Onions are especially common in Indian food. But they pop up in cuisines all around the world and it’s likely that anyone who’s ever done a bit of cooking has at least chopped an onion – and cried over a chopping board too! 

There isn’t just one way to cook onions, so this will entirely depend on the recipe and type of food you’re making. Some recipes will call for browned onions, while others will not. Think about the dish you want to end up with and this will help to guide how you cook your onions - make sure you know which before heating up the pan.

If you’re after a deeper flavour, which is often the case with curry sauces, then you’ll want to brown your onions. Getting this right can be tricky as you’ll want to make sure you get an even browning without any burning. Onions can be a bit tricky. Whether it’s struggling to cut them to the right shape, to making sure they don’t burn and stick to the pan. Onions are such a crucial ingredient, it’s important to get them right. So here are my top tips to help you on your way.

Chopping Onions

The first step is learning how to prepare your onions before they even get close to the heat. The more experienced chef will have their technique down perfectly and will be able to show it off with some speed – although this guy puts many of them to shame in bravery alone. But being quick is no substitute for getting it right!

Whether you’re slicing or dicing onions, there’s a quick and safe technique that leaves you with nice, even results. I put this video together to demonstrate:

It’s important that you choose the right knife for the job – in this case, a Chef’s Knife – and that you use the proper knife techniques to stay safe and efficient. Also, remember to always keep your knife as sharp as possible, as a blunt knife is not only harder to use, but also far less safe.

Tears

We’ve all cried a tear or two over an onion and there are some weird and wonderful ways to try and avoid this. But if you’ve ever wondered why we cry in the first place, then here you go… When you cut an onion you damage the cells, and the onion releases volatile gases, These set off a series of chemical reactions that result in a gas called propanethial S-oxide being released. This gas irritates our eyes and our body reacts by releasing tears to dilute the gas, hence we cry. On the plus side, the more often you chop onions the amount of eye irritation is reduced – so the more you cook the less you’ll sob!

There are plenty of old wive’s tales about how to cut onions so your eyes don’t water, from holding your breath to cutting onions with a spoon in your mouth (seriously!) to even chewing a raw onion while you chop. None of which make any sense to me. Someone told me once to put a lit match in my mouth while cutting but I couldn’t see how setting fire to my eyelashes would help.

Anyway here are a few tips and suggestions that might be more useful:

1. When peeling and chopping the onion, leave the root on.

2. Use a sharp knife to cut – this causes less cell damage so fewer irritants will be released.

3. Once cut, turn the onion over so the flat side sits on the chopping board and once chopped, move the onions into a prep bowl, or to a pan with a lid.

4. Chill your onions as this slows the release of the irritant. If all else fails, invest in some onion goggles! 

Cooking Onions

Many dishes require onions to be diced, and it’s really important that you chop them all the same size so they cook at the same speed and in the same way. Start by heating your pan and oil on a high heat then add your onions. Make sure you stir them well so they are exposed to the heat evenly. Then after few minutes, the residual water will evaporate and the onions will become translucent. If you’re adding more vegetables than add them at this stage. This gives you a solid base which doesn’t have a strong onion flavour, but will have a nice depth.

For dishes that need a more robust onion kick, like a Jalfrezi or a stir fry, then cut your onions into slices or chunks. Then cook them more quickly on a higher heat so they retain their crispiness and give an even richer onion flavour.

For other dishes where you are looking for a greater depth, then cook the onions low and slow for a long time. Cooking them like this means they lose all of their astringent qualities and become completely browned, tender, sweet and delicious.

The truth about caramelisation

Many recipes call for your onions to be caramelised, this is what happens to sugars at relatively high temperatures. When you're browning onions, no matter how you do it, you rarely reach the temperatures necessary for caramelisation. The browning of the onions is a result of the Maillard reaction. This is the reaction between sugars or other carbohydrates and amino acids and the heat. Maillard flavours are more complex and "meaty" than caramelised flavours.

Recipes that call for adding sugar to the onions and cooking at higher temperatures may result in a little true caramelisation, but it's negligible compared to the Maillard reaction. Just to be clear sweeter variety of onions have no more sugar than then other onions (Know Your Onions) so they are not going to caramelise either.

In fact sweeter onions are not a good choice when it comes to dishes where you want depth and earthiness. These onions contain less sulphur compounds so when it comes to browning them over a long period they end up with a slight sweet flavour but lack the complexity you get from a browned onion that is more astringent. The sulphur compounds in onions are the irritants that make us cry when they raw. It's these that are the key components required to give the crucial flavours we are looking for when we brown our onions. They change during the cooking process and give us an amazing depth and intensity. 

How to Brown your onions

There are two main methods of browning your onions which give slightly different results.

1. Slow cooking - this results in the cells of the onions breaking down so they form a paste. The onions brown slowly and evenly, almost from the inside out. As they break down they reduce in volume and result in a wonderful intensity which is perfect for a masala base.

2. Higher temperature browning - The onions cook more quickly over a higher heat so that they brown before they have a chance to break down. The onions end up brown but they retain their shape and texture.

A great little time saving tip is to make batches of browned onions and freeze them - you can then defrost and use as and when you need it.

Indian Cooking

When it comes to Indian cooking it’s all about the onions. These form the basis of your masala sauce and if you take time to cook the onions correctly, then the rest of the dish will just follow easily. So for a great curry follow my three simple rules:

Meat dishes

1. When cooking a meat curry where you are looking for a deep, rich, intense, tomato based sauce the depth will comes from cooking your onions low and slow until they’re a dark drown colour. The onions will go through a few phases, first becoming translucent and then browning fairly quickly. Keep watching and be sure to keep stirring to make sure everything is cooked evenly. If you find that your onions are catching on the bottom of the pan then just add a little splash of water and stir. The longer you leave them to cook and brown the darker the colour of your dish will be so for a really rich dark brown masala, I usually cook the onions for a good 30 minutes.

For dishes such as Thari Wala Chicken or Lamb Bhuna this will ensure that the masala sauce is thick and full of flavour.  

2. When cooking a meat dish with what I would call a white sauce, such as a Chicken Korma one that has a creamy finish and is either yoghurt, cream or coconut based. These sauces are lighter in colour and flavour so the onions need to be chopped much finer and cooked until they only just turn golden.

Vegetables or Lentils

3. These ingredients require an overall lighter flavour where the textures and flavours of the vegetables are more dominant so the base needs to be lighter. Ideally I would only sauté the onions on a higher heat for about 15-20 minutes to soften them until they just begin brown.

Using ghee rather than oil makes things a bit quicker, as ghee can reach a higher temperature than oil, so the onions will cook faster. If you’re inexperienced, you should only really do this when browning as it will mean keeping a very close eye to ensure nothing’s burnt.

It’s impossible to achieve a rich, thick curry sauce without properly browned onions, and undercooking is one of the most frequent mistakes made by curry novices. Generally you should fry onions for at least 30 minutes to make sure they’re properly browned. This seems like a long time, but trust me, the results are worth it!

Put your skills to practice!

What better way to test out your new found onion mastery than with the double onion curry, AKA Dopiaza.