Melt butter, let rest for 5 minutes before starting sauce. In a bowl (that will be placed over a small saucepan of simmering water) place your Egg Yolks, Vinegar, lemon juice and seasonings. Whisk until the egg mixture starts to thicken and create pale yellow ribbons, if your egg mixture starts to scramble remove from heat and add a dash of lukewarm water to slow the cooking process. When your egg mixture has doubled in volume, remove from heat and slowly start to beat in the melted butter. Mix in prepared Horseradish sauce and keep warm until ready to serve.