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Clarified butter is butter which is melted and made clear by separating and then discarding the milk solids. More specifically, by melting butter, a cook can see that it separates into clear golden liquid and a thick liquid which settles to the bottom.
The thick liquid is composed of milk solids, a protein-rich solution that burns easily over high heat. So, once the milk solids are separated and removed, the remaining butter can be cooked on a very high heat without burning.
Clarifying butter is very easy. Slice 1 stick of butter into small pieces. Heat the butter slices in a heavy saucepan over low heat until it crackles and bubbles. Remove the pan from the heat and use a spoon to carefully skim off the fat foam that has risen to the top. Pour or spoon the clear liquid into a container, leaving the thicker milky stuff at the bottom. Discard the white residue. Tightly cover the liquid and refrigerate or freeze. It can be easily be stored either way for months.