Cut softened butter into thirds. In the top of a double boiler, combine beaten egg yolks, water, lemon juice, salt and white pepper. Add a piece of the butter. Place over boiling water (upper pan should not touch water). Cook, stirring rapidly with a whisk, until butter melts and sauce begins to thicken. Add the remaining butter, a piece at a time, stirring constantly until melted. Continue to cook and stir until sauce thickens (about 2 minutes more). Immediately remove from heat. If sauce is too thick or curdles, immediately whisk in 1 to 2 tablespoons hot water. Makes 3/4 cup sauce.