I've been hooked on using brown butter in baking ever since I first made it, and it's one of those shortcut ingredients to great cooking. It takes cake to a whole new level of complex, nutty deliciousness, and adds toasted flavors to blondies, cornbread, or even savory dishes like pasta and risotto.
Every self-respecting home baker should know how to brown butter, especially considering there's nothing to it. If you have butter, a pan, and a rubber spatula, you're good to go.
Step One: Heat Butter in a Light-Colored Pot
Butter consists of clear yellowish butterfat, water, and milk proteins. When browning butter, those proteins are what's actually browning. I start by plopping the desired amount of butter in a heavy-bottomed and preferably light-colored saucepan. The heavy bottom ensures the butter heats evenly while the light color allows you to monitor the butter's color as it browns.
Heat the butter gently over low heat until it has melted completely.
I usually stir the butter with a rubber spatula all through the browning process, which also helps it melt evenly.
Step Two: Cook Off Water
Butter contains a good 13 to 17% water, which has to go before the fat's temperature can rise enough to brown the milk proteins. Once the butter reaches a temperature of 212°F, the water in the butter starts to evaporate much more quickly. As a result the butter will start to bubble and splatter dramatically. I usually place a splatter screen over the pan at this point, though swirling the pan and stirring constantly to make sure any and all bubbles get released will work as well.
If you're confident, you can raise the temperature to medium or medium-high at this point, though higher temperatures means your butter will go from perfect to burnt much faster. Make sure to scrape the sides and bottom of the pan to prevent the butter from catching and burning.
Step Three: Brown the Milk Solids
After about five minutes the butter will start to foam. This is when you want to watch the butter like a hawk, stirring it around with your spatula to prevent the milk solids from sticking to the bottom of the pan.
You can tell the butter is browning because dark golden flecks (browned milk solids) will appear in the melted butter, which will start to smell nutty and toasty.
The foam can make it hard to see if the butter is browned to your liking, so to check the color, try clearing away some of the foam with a spoon or take the pan off the heat and spoon a little of the butter onto a white plate.
Once you're happy with the level of browning, pour the butter—browned milk solids and all—into a heatproof bowl and stir it for one or two minutes to cool it down. If you were to leave the butter in the pan, the residual heat would continue to cook it, and the butter might scorch from a perfect brown to a burnt-tasting black.
Also, keep in mind that only the milk solids turn a dark golden brown, not the butter itself. The fat will be darker as well, but not as dramatically as the milk solids.
The hot melted butter can be used immediately in savory dishes (try drizzling it over pasta), or chilled to cream into cookies and cakes.