Add the butter to a medium size pan over low heat and cook until melted, do not burn it.
Pour in the flour and immediately whisk it over low heat until combined and cook for 2 minutes to form a white roux. Cool until ready to use.
For a blond roux continually whisk it over low heat for 10-15 minutes or until it begins to darken and is light caramel in color. Cool until ready to use.
For a dark roux continually whisk over low heat for 30-35 minutes or until it is very dark brown in color. Cool until ready to use.
