1 medium to large onion, thinly sliced
1 cup sliced mushrooms
dash of salt
1 tsp berry-balsmic vinegar
4 slices medium thick sliced cheese of your choice
8 slices sourdough bread
1 tsp melted butter
In a skillet, melt the 2 tbsp butter and add onion. Saute the onion for about 10 minutes until onion is soft and golden brown. Stir in the mushrooms and cook for a couple of minutes more. Remove from heat. Sprinkle with a dash of salt and add vinegar. Place cheese on 4 slices of the sourdough bread. Top the cheese with the onion and mushroom mixture. Top with remaining sourdough bread slices. Brush bread with the melted butter and cook over medium heat in a skillet or griddle 2 to 3 minutes per side to melt cheese.