What's Fabulous: Garum
Garum, also known as colatura, is an intensely flavored seasoning made from fermented anchovies. Salty and a bit pungent, it is pure umami. With a thin, watery body, garum is very similar to fish sauce used in many Asian cuisines, but garum is more concentrated. And more expensive.
Originally from Rome and southern Italy, it's been made for centuries and today is still produced in Cetera, a small town south of Naples.
Food historians have found proof of garum being used by wealthy Romans to season just about anything they ate. For us it's instant umami -- that fifth taste that so many of us love (the other four being sweet, salty, sour and bitter). Add a little garum to salad dressing, especially for a Caesar salad, to sauces and gravies, to risotto, or just sprinkled on a plate of sliced tomatoes, and you'll get a flavor boost.
Cooking With Colatura
The most common way to use garum is in pasta sauces, sometimes replacing sautéed anchovies as you can do with a classic puttanesca sauce if you leave out the anchovies and instead add a teaspoon or so of garum.
In this 2003 New York Times article, Melissa Clark provides more background, with the help of Italian food expert and author Arthur Schwartz. She also offers a recipe that showcases the garum. See the link below for the article and recipe.
Here is another recipe, this one for a white bean salad from Food52. When making this salad, I would begin with about 2 teaspoons of garum, knowing you could always add more. I also might do half garum and half red wine vinegar.
You can use colatura interchangeably with the easier-to-find and less costly fish sauce, EXCEPT you need to adjust for quantities as garum is less salty yet also more intense. Both fish sauce and garum have the same watery body which means to achieve the same degree of flavor you'll need to add far more fish sauce, which can wreck a recipe (1 tablespoon of garum is about equal to the flavor of a half-cup of fish sauce). The reverse is also true if you're using fish sauce in a salad dressing or marinade; garum will give you the taste but you'll need another liquid to create the necessary volume.
I also think garum is more complex and less salty than fish sauce, but taste for yourself to decide.
Moreover, instead of thinking of garum and fish sauce as interchangeable, I think a better comparison is garum with anchovy paste. But the garum will mix and dissolve more easily than the anchovy paste while providing a similar salty and umami taste.
If you take a whiff of an open bottle of garum, don't be put off by its fishy aroma. Once added to food it adds a splendid complexity.
Buying Garum Colatura
Garum is not easy to find, certainly not as easy as fish sauce or anchovy paste. But it's worth the search. When making your search look for it under both names: garum and colatura because I found there's no pattern to a preferred name.
In NYC you can find it at Buon Italia in Chelsea Market. A 100 ml bottle I recently bought cost $11.95.
Online you can find it at Gustiamo.com (an online but NYC-based Italian grocer that offers a superb product selection) and at Zingermans.com. Prices and brands vary but be sure you're getting garum made in Cetera.