Put the grated horseradish into a small earthen cooking vessel; add the flour, salt, paprika and butter; pour in the cream and let cook until thick and smooth. Keep stirring constantly. Move to the back of the stove and add the egg yolk, stirring rapidly. Cook for 30 seconds and serve at once. This sauce may be eaten as a relish with hot roast or boiled beef. Source: Pennsylvania Dutch Cook Book - Fine Old Recipes, Culinary Arts Press, 1936.