CopyCat: Durkee's-Style Famous Sauce

1/2 cup Cold water
4 tablespoons Cornstarch
1/2 cup Dark vinegar, plus 2 tbsp.
2 tablespoons Salt
1/2 cup Sugar
1 Egg
4 tablespoons Prepared mustard
4 tablespoons Margarine, cut in tiny bits

Place all ingredients as listed in blender on high speed until smooth (2 minutes). Transfer to top of double boiler and cook over gently boiling water, stirring often for 12 to 15 minutes or until thickened and smooth. Once more put mixture back through blender 30 seconds or till smooth, using high speed.

Refrigerate in covered container 24 hours before using. Keep refrigerated 3 months. If giving as a gift, be sure to include an expiration date on the jar/container.