The best way to appreciate the value of fat in the kitchen is to try to imagine cooking without it. What would vinaigrette be without olive oil, sausage without pork fat, a baked potato without sour cream, a croissant without butter? Pointless, that’s what. Without the flavors and textures that fat makes possible, food would be immeasurably less pleasurable to eat. In other words, fat is essential for achieving the full spectrum of flavors and textures of good cooking.
Besides being one of the four basic elements of good cooking, fat is also one of the four elemental building blocks of all foods, along with water, protein, and carbohydrates. While it’s commonly believed that fat, much like salt, is universally unhealthy, both elements are essential to human survival. Fat serves as a crucial backup energy source, a way to store energy for future use, and plays a role in nutrient absorption and essential metabolic functions, such as brain growth. Unless you’ve been directed by your doctor to strictly reduce your fat consumption, you don’t need to worry—there’s nothing unhealthy about cooking with moderate amounts of fat (especially if you favor healthy plant- and fish-based fats).
Fat plays three distinct roles in the kitchen: as a main ingredient, as a cooking medium, and, like salt, as seasoning. The same type of fat can play different roles in your cooking, depending on how it is used. The first step in choosing a fat to use is to identify the primary role it will play in a dish.
Used as a main ingredient, fat will significantly affect a dish. Often, it’s both a source both of rich flavor and of a particular desired texture. For example, fat ground into a burger will render as it cooks, basting the meat from within and contributing to juiciness. Butter inhibits the proteins in flour from developing, yielding tender and flaky textures in a pastry. Olive oil contributes both a light, grassy flavor and a rich texture to pesto. The amount of cream and egg yolks in an ice cream determine just how smooth and decadent it’ll be (hint: the more cream and eggs, the creamier the result).
The role fat plays as a cooking medium is perhaps its most impressive and unique. Cooking fats can be heated to extreme temperatures, allowing the surface temperature of foods cooked in them to climb to astonishing heights as well. In the process, these foods become golden brown and develop the crisp crusts that so please our palates. Any fat you heat to cook food can be described as a medium, whether it’s the peanut oil in which you fry chicken, the butter you use to saute spring vegetables, or the olive oil in which you poach tuna.
Certain fats can also be used as seasoning to adjust flavor or enrich the texture of a dish just before serving: a few drops of toasted sesame oil will deepen the flavors in a bowl of rice, a dollop of sour cream will offer silky richness to a cup of soup, a little mayonnaise spread on a BLT will increase its succulence, and a smear of cultured butter on a piece of crusty bread will add untold richness.
To determine which role fat is playing in a dish, ask yourself these questions:
Will this fat bind various ingredients together? If so, this is a main ingredient.
Does this fat play a textural role? For flaky, creamy, and light textures, fat plays the role of main ingredient, while for crisp textures, it’s a cooking medium. For tender textures, fat can play either role.