Place the water, honey, red wine vinegar, and Dijon mustard in a mixing bowl. Using a wire whisk, mix the ingredients well. Add the cornstarch and whisk until smooth.

Place the bacon grease in a saucepan over medium-high heat. Add the onions and sauté until golden brown. Add the honey vinegar mixture and continue stirring until the mixture thickens and comes to a boil. Remove from heat.

Refrigerate in an airtight container until needed. Use a double boiler to reheat.