Put the butter in a small, heavy-bottomed saucepan over medium heat. In about 10 minutes it will be frothy and bubbling. When the froth starts to subside slightly, turn down the heat to low and watch the butter closely. Prepare a bowl of cold water large enough to fit the bottom of the saucepan. As the butter cooks, check the bottom of the saucepan by tilting it and seeing if any specks of brown coagulated milk solids are adhering to it. After 15 to 20 minutes total cooking time you’ll see the milk solids coagulate into white specks and within a minute or two these specks will turn pale brown and then deep brown. As soon as they turn deep brown, dip the bottom of the saucepan in the bowl of cold water for a few seconds to stop the cooking. Pass the butter through a strainer lined with a triple layer of cheesecloth, paper towels, or a clean kitchen towel (not terrycloth, however, or it will absorb too much butter). The butter should have a lovely nutty fragrance. Store, well covered, in the refrigerator.