This is not the original dressing that I was looking for (BIH, my restaurant, uses salt and no mustard), but it IS still delicious! Definitely one of my favorite dressings!
1/2 lb. bacon
2 cups water
3/4 cup vinegar
1 cup sugar
1 heaping TBSP. prepared mustard
3-4 TBSP. flour
Fry, drain, and crumble bacon. Combine all ingredients in a saucepan. Bring mixture to a boil. Lower heat, stirring until mixture thickens. Remove from heat and stir in bacon pieces. Serve warm over lettuce or fresh spinach.