Spinach Salad with Warm Bacon Vinaigrette

For the salad: 

baby spinach leaves, rinsed and dried

button mushrooms, thinly sliced

hard boiled eggs, peeled and sliced

medium red onion, thinly sliced

For the dressing: 

slices thick bacon (about 6 oz.), finely diced

cup red wine vinegar

honey or sugar

Dijon mustard

Salt and pepper,