The Century Cook Book circa 1894
(To serve with roast beef)
You need four tablespoonfuls of grated horseradish, 1 teaspoonful of pounded(powdered) sugar, 1 teaspoonful of salt, 1/2 teaspoonful of pepper, 2 teaspoonfuls of made mustard, vinegar.
Grate the horseradish, and mix it well with the sugar, salt, pepper and mustard; moisten it with sufficient vinegar to give it the consistency of cream, and serve in a tureen; 3 or 4 tablespoonfuls of cream added to the above, very much improve (sic) the appearance and flavor of this sauce.
To heat it to serve with hot roast beef, put it in a Bain Marie(double boiler), or a jar, which place (sic) in a saucepan of boiling water; make it hot, but do not allow it to boil, or it will curdle.
NOTE- This sauce is a great improvement on the old fashioned way of serving cold scraped horseradish with hot roast beef. The mixing of the cold vinegar with the warm gravy cools and spoils everything on the plate. Of course, with cold meat, the sauce should be served cold.