Mom's Old Fashioned Homemade Mustard

From the kitchen of Kevin Taylor, the BBQ Guru

1/2 cup dry mustard
1/2 cup cider vinegar
1/2 cup granulated sugar
1 egg, beaten
1 teaspoon cornstarch
1 cup mayonnaise (NOT Miracle Whip)
Dash of salt

Mix mustard with vinegar and refrigerate overnight.

Bring to room temp and cook with beaten egg, sugar, salt and cornstarch. Cook slowly, stirring constantly, till boils and thickens. Cool.. add mayo...refrigerate.