Butter used should always be the real thing, the best quality, no gruesome replacements such as margarine or baking spread!
Clarified butter is called for in some recipes: this is butter from which all milk solids have been removed by heating it. The result is a clear butter that can be heated to a higher temperature, which makes it ideal for frying. To clarify butter, heat unsalted butter in a saucepan over very low heat until it is melted. Let it gently simmer until a froth rises to the top and use a spoon to skim off the froth. You will notice a milky layer in the bottom of your pan. Carefully pour the clear liquid above it into a heatproof storage container, discarding the froth and the milky residue. Clarified butter keeps quite a long time in the fridge, and you can also freeze it.