Prep Time: 15
Cook Time: 10
Serves: Serves: 4
Melt butter over medium heat in large skillet. Add bell pepper, cook 4 minutes. Stir in mushrooms and garlic, cook 6 minutes or until pepper is tender and liquid from mushrooms evaporates. Season with salt and pepper to taste.
Meanwhile, spread bread with mustard, mayonnaise and/or horseradish sauce to taste.
Layer lettuce, tomato and onion, if desired, over bottom half of loaf. Top with mushroom mixture, cheese and avocado. Cut crosswise into fourths and serve.