Mustard Sauce 1/4 cup sugar 1/4 cup milk 1/4 cup white/cider vinegar 2 tbs dry mustard 1 egg pinch salt 2 tbs butter Crack the egg into the top of a double boiler and whisk until beaten. Add sugar, milk and mustard, whisk well. Cook over simmering water for about 5 minutes, until sugar and mustard are dissolved and mixture is hot, stirring occasionally. Add vinegar and continue to cook until thick. Remove from heat, stir in butter and salt. Refrigerate.