A staple of Indian cooking, ghee is made by slowly cooking whole sweet butter until the water contained in the butter evaporates and the milk solids turn golden brown, giving the butter a rich, nutty aroma and flavor. Surprisingly little ghee can be stirred into soups just before serving to give them a rich, buttery flavor.
Because butter is about 25 percent water, it takes about a pound (2 cups) of butter to make 1-½ cups of ghee. If you use ghee with any regularity, it’s worth using at least a pound of butter and keeping the ghee in a plastic container in the refrigerator, where it will keep well for at least 6 months; in the freezer it will keep indefinitely.
Although ghee can be used alone as a flavorful finish for Indian and other soups (it’s especially good in bean soups), most Indian cooks flavor it by using it to fry spices and flavorings such as garlic, onions, ginger, and chilies. This aromatic spiced ghee—called tadka—is then stirred into soups and other dishes as a last-minute flavoring.