Place the mustard in a mixing bowl or the bowl of an electric mixer. Add the mayonnaise and beat for 1 minute.
Add the Worcestershire, A-1, cream, and a pinch of salt and beat until the mixture is well blended and creamy. If you'd like a little more mustardy bite, whisk in about 1/2 teaspoon more dry mustard until well blended. Chill the sauce, covered, until serving.Makes 1 cup Source: