For salad, in a large salad bowl, combine spinach (or spinach and sorrel) and mushrooms; set aside.
For dressing, in a very large skillet, cook bacon over medium heat till crisp. Using a slotted spoon, remove bacon, reserving 2 tablespoons drippings in skillet (add olive oil, if necessary to measure 2 tablespoons). Drain bacon on paper towels; set aside.
Add onion and garlic. Cook and stir over medium-low heat till tender but not brown. Stir vinegar, sugar, bouillon granules and black pepper into the drippings. Bring to boiling; remove from heat. Add the spinach mixture. Toss mixture in the skillet for 30 to 60 seconds or till spinach just starts to wilt.
Transfer mixture back to salad bowl or to individual plates. Sprinkle with bacon and chopped egg. Serve immediately. Makes 4 to 6 servings.