This will keep refrigerated for up to 3 months.
- 1/2 cup cold water
- 4 tablespoons cornstarch
- 1/2 cup plus 2 tablespoons dark vinegar
- 2 tablespoons salt
- 1/2 cup granulated sugar
- 1 egg
- 4 tablespoons prepared mustard
- 4 tablespoons margarine, cut into tiny bits
- Put all the ingredients into a blender and blend until very smooth.
- Put blender contents in top of double boiler and cook over gently boiling water, stirring often for 12 to 15 minutes, until thickened and smooth.
- Return mixture to blender and blend at high speed for 30 seconds or until smooth.
- Put sauce into a covered container and refrigerate for 24 hours before using.