If you crave a savory, warm snack, you will love the addition of fresh mushrooms and caramelized onions to your sourdough bread. Brown the mushrooms in a pan, remove the mushrooms and then add your sliced onion. Caramelize the onions with 1-2 teaspoons of sugar and 2 teaspoons of water. Keep them in the pan for about 5 minutes and then add them to your mushrooms. Voila!