Traditional hollandaise sauce contains refined butter, egg yolk, chopped onions, lemon juice, salt, white wine, vinegar, white pepper, parsley stems, and salt. The recipe is to boil down white wine in a pan, then boil down the onion, pepper, vinegar, and parsley stems over low heat. For butter, use purified butter melted at room temperature or melted butter by turning it into a lens. Add egg yolk and butter, stirring well, continuously adding butter little by little. When the sauce is thick, add the boiled wine and adjust the concentration. And finally, if you season it with salt, you can make authentic hollandaise sauce.