Cook bacon in a large skillet until lightly browned; remove and crumble. Pour off all but 1 tablespoon bacon fat.
Add onion to skillet and cook until tender, about 5 minutes. Add mushrooms and cook 5 minutes. Blend in flour, dry mustard, salt and TABASCO® Sauce; stir in water and vinegar.
Cook, stirring constantly, until mixture thickens and comes to a boil. Add spinach and mix well. Transfer to a serving bowl and sprinkle with crumbled bacon.
Makes 4 servings.