First Things First

To harness the magic of butter, you need to know its parts and how those parts work. Butter is primarily milk fat, 80 percent usually. The fat is what contributes great flavor and texture to so many foods. This fat is hard and opaque at room temperature but melts into translucency. When the fat is separated from the other components of butter, it can be heated to 400°F/200°C before it starts to smoke, which makes it a superlative medium for cooking. Butter fat will do things that other fats do—shorten or make more tender a dough or pastry crust, add richness and flavor to a sauce, or be the main component of a sauce. Water makes up about 15 percent of butter. This is why butter is soft and spreadable at room temperature; pure butter fat is not. Water is what makes it froth when you heat butter in a pan, and it is what keeps the pan cool. The remaining weight of butter is composed of solids (proteins, salts, lactose). Once the water has been cooked out of butter, these solids become brown and flavorful, but they can turn black and bitter if you cook them too long.