In the world of cooking fats, butter is the odd one out. Most of the other fats we cook with, like vegetable oils and lard, are nearly 100% fat, while butter is an emulsion of about 80% fat and 15% water, with the remainder made up mostly of milk proteins. Some of butter's best qualities are the result of its composition—those dairy proteins give butter much of its excellent flavor, and because butter is already an emulsion, it can be emulsified into things like pan sauces more easily.
There are a few potential downsides, though. First, butter has a very low smoke point, thanks once again to those milk proteins, which can quickly burn if the butter gets too hot. (And no, you can't raise butter's smoke point by mixing it with oil.) Its water content, meanwhile, means it's more prone to rancidity than purer oils.
Enter clarified butter: When we remove the milk proteins and water, what we're left with is almost 100% pure butterfat, with an exceptionally high smoke point (about 450°F, compared to about 350°F for regular butter) and a long shelf life, though, admittedly, a slightly more subdued butter flavor. Clarified butter allows us to sear meats and vegetables in butterfat with no worry about burning, and it can keep in the fridge for months on end without developing any off flavors.
The first step when making clarified butter is to melt unsalted butter, which breaks the emulsion—the water sinking to the bottom of the pot, and the milk proteins turning to a white foam on the surface.
At this point, the most common technique, and the one used at many restaurants, is to skim the foamy milk proteins from the surface, then ladle off the pure butterfat without collecting any of the water at the bottom. This method is very quick and works great for clarifying larger quantities of butter, but it isn't ideal at home, when you're likely clarifying a pound or less at a time. That's because all that skimming and ladling inevitably translates to lost yield, since you're bound to remove some butterfat with the foam and leave even more behind with the water.
Instead, I recommend that home cooks use the clarification method most commonly associated with ghee—Indian clarified butter. The main difference is that to make ghee, instead of melting the butter and then manually separating its parts, we boil off the water completely and allow the milk proteins to brown, then strain the proteins out at the end. As an added benefit, browning the milk proteins gives the finished clarified butter extra depth, with a subtle nutty flavor.
To clarify butter at home, start by melting unsalted butter in a saucepan.
Once it's fully melted, allow it to continue to heat until it comes to a gentle boil. The milk proteins will first form a thin white layer over the entire surface, then expand into a thicker foam. Eventually, as the butter boils, the foam coating will break apart into smaller clusters. Technically, it's not the butterfat but the water in the butter that's boiling—that's a good thing, since we want the water to cook off.
The foam will ultimately sink to the bottom of the pot as the butter continues bubbling away. You'll know that it's nearly done when the bubbling activity calms and then mostly ceases, evidence that the water is finally gone.
At that point, just pour the remaining butter through cheesecloth or a coffee filter to remove the browned bits. And there you have your clarified butter—no longer quite as flavorful as regular butter, but also not nearly as fragile.