Yes, you should clarify the butter before using it in hollandaise sauce. Clarified butter, also known as ghee, removes milk solids and water, resulting in a smoother, more stable sauce.
Hollandaise sauce is an emulsion of butter, egg yolks, and lemon juice (or vinegar). The presence of milk solids and water in whole butter can destabilize this emulsion, leading to a grainy or broken sauce. Clarifying the butter involves melting it slowly and allowing it to separate into three layers: foam (milk solids), clear butterfat, and watery liquid at the bottom. The clear butterfat is carefully skimmed off, leaving the milk solids and water behind. This clarified butter is almost pure fat, which contributes to a smoother, richer, and more stable hollandaise. Using clarified butter also gives the hollandaise a cleaner, more buttery flavor, as the milk solids can sometimes impart a slightly browned or nutty taste that isn't always desirable in this delicate sauce.
When clarifying butter, melt it over low heat to prevent the milk solids from burning. Burnt milk solids will impart a bitter taste to the clarified butter, ruining its flavor and making it unsuitable for hollandaise.