Divide spinach on to 4 plates. Top each salad with 2 sliced mushrooms, 2 hard boiled eggs, quartered, half a slice of sweet red onion, separated into rings, and 1/4 cup croutons.
Drizzle with hot bacon dressing to taste and serve immediately.
Brown bacon until well done; add onions. Saute until onions are translucent.
Add remaining ingredients and bring to a boil. Cook for 5 minutes, until somewhat thick.
Makes almost 1 quart.
Refrigerate leftover dressing and warm before using again.