Despite being all the rage in restaurant kitchens across the world today, ferments have been around for millennia. What started as a necessary technique to preserve food for longer is now something most of us enjoy for the flavours it adds to ingredients. And while we’ve heard of fermented foods like kimchi, sauerkraut and miso, garum doesn’t enjoy the same sort of popularity in the home kitchen. However, many of us have actually tasted it before, or at least something comparable, without realising.

Packed full of rich umami – as all the best ferments are – garum is at its core a liquid seasoning made from the liquid fish expels as it ferments. It’s a similar product to the likes of fish sauce or even the UK’s Worcestershire sauce, which is also made from fermented anchovies. Over the years it has also been referred to as the ‘Roman ketchup’ due to the way it used to be liberally applied to any and all savoury dishes in Ancient Rome. These days, however, garum is used with a lighter touch, often as a seasoning to bring out the savoury notes of ingredients as well as adding further depth.

When garum started growing in popularity around the first century AD, it was made by combining the entrails of various fish with salt and fresh herbs, which were then left to ferment for up to three months before being pressed with stone to extract the liquid. Different grades of garum would then be produced, ranging from weaker products diluted with water or oil, to thick pastes made by evaporating concentrated garum for a rich umami depth. Its popularity meant small garum factories began popping up across the Roman Empire, which are still being discovered by archaeologists to this day. For years it was even used as a medicine to ease ulcers and dysentery. When the Empire fell, however, garum production ceased almost completely and this once household essential all but vanished for years to come.

While garum production was thriving in Europe during the Roman period, a very similar condiment was proving popular in Asia – what we know today as fish sauce. There’s evidence that sauces made from a combination of fermented fish guts and soy beans were being used as condiments in China as far back as 300BC. However, over the next few hundred years, soybeans started to be favoured more in China (leading to the creation of soy sauce), while in places like Vietnam and Thailand, fish became the chosen fermented protein. This distinct split in favoured condiments remained relatively clear-cut until the seventeenth century, when traders began to bring food up to China from the South. However, soy sauce is still strongly associated with China, whilst fish sauce is more commonly used in Southeast Asian cuisines.

The fish sauces of Southeast Asia, often strongly flavoured and made from anchovies, are often regarded as the closest thing we have to traditional garum today, although we tend to use it more as a cooking ingredient than a condiment. However, something thought to be an even closer relative of traditional Roman garum is Campania’s Colatura di Alici. Made from just two ingredients (salt and anchovies), the fish are left to ferment for weeks until the liquid can be drained off. It’s believed that Colatura tastes very similar to the garums of Ancient Rome and is generally used in the same way (as a condiment rather than a cooking ingredient).

The story of this historic seasoning doesn’t stop here. With a new wave of fermentation-obsessed chefs spearheading new and rediscovered ways of incorporating ferments into their dishes, garum is evolving. With waste reduction and sustainability more important than ever for restaurants, chefs have found ways of making garum without having to buy in anchovies – or even any fish at all.

René Redzepi, the chef at Copenhagen’s legendary restaurant Noma, is generally credited with leading the modern-day resurgence and reinvention of garum by using proteins such as bone marrow and even grasshoppers as the base. He realised that due to the nature of the fermentation process, which traditionally would involve the enzymes in the fish guts breaking down the protein, he would need to use something else to trigger the fermentation. The answer to his problem? Koji – the fungus used in the production of everything from sake to miso. Along with salt, rice grains inoculated with koji spores are added to the fermenting mixture to do the job of the enzymes, meaning that almost anything containing protein could be turned into garum.

Chefs and fermenting-obsessives alike have now attempted to make koji-triggered garums out of everything from bee pollen to Guinness, all of which are subtly distinct in flavour but have the same whack of umami that the seasoning is known for. What’s more, these new-wave garums are being used in a whole host of different ways in restaurants. Some chefs add it to their braising liquids to give meat an extra intensity; others use it as a condiment in the place of soy sauce. Meanwhile, more and more Italian chefs are using their beloved Colatura di Alici to invigorate pasta sauces or drizzling it over pizza.

Garum is a fantastic example of an ingredient which has been around for centuries yet is still evolving and being used by chefs in contemporary restaurants to this day. If you’re a keen fermenter looking to up your umami game in the kitchen, why not try experimenting with your own garums? All you need are a few ingredients on top of your chosen protein – along with a lot of patience.