A delicious side dish or a simple lunch or dinner.
In a skillet cook bacon until done.
Remove from pan reserving 2 tablespoons bacon grease for dressing and 2 tablespoons or so for cooking onion and mushrooms.
Cook onion and mushrooms in 2 tablespoons bacon grease until onions and mushrooms are tender. Or until desired doneness.
In a small bowl whisk together remaining two tablespoons bacon grease, red wine vinegar, mustard, and salt.
In a large bowl combine spinach, onion mushroom mixture, and dressing. Carefully stir just until well combined.