Melt the butter in a heavy saucepan over medium-low heat. When the butter looks clear, cook, watching carefully without stirring, until the solids begin to brown. Move aside any foam that forms in order to check the progress of the solids. (If necessary, skim off some of the foam and discard it.) When the bubbling noise diminishes, all of the water has evaporated, so the butter can burn easily. Strain the butter immediately through a fine-mesh strainer or cheesecloth-lined strainer. If time allows, instead of straining the butter, simply pour it into a container and allow it to set. The milk solids will settle to the bottom and can be removed easily by reheating the butter and pouring off the clear portion.