Mushroom Grilled Cheese Sandwich

 1 tablespoon butter
  1 tablespoon olive oil
1 small onion, sliced
8 ounces cremini mushrooms, sliced
2 cloves garlic, chopped
1 teaspoon thyme, chopped
1/4 cup white wine or broth
  salt and pepper to taste
1 tablespoon parsley, chopped
  1/2 teaspoon truffle oil (optional)
1 cup fontina or gruyere, shredded
1/4 cup parmigiano reggiano, grated
4 slices bread
  2 tablespoon butter

-Melt the butter and heat the oil in a pan over medium heat.
-Add the onion and saute until tender, about 5-7 minutes.
-Add the garlic and thyme and saute until fragrant, about a minute.
-Add the cremini mushrooms and saute until the start to caramelized and turn golden brown, about 10-15 minutes.
-Add the wine, deglaze the pan and cook until most of the liquid has evaporated, about 2-3 minutes.
-Season with salt and pepper, add the parsley and remove from heat and let cool a bit.
-Mix the cheese into the mushrooms.
-Butter one side of each slice of bread and place 2 in the pan buttered side down.
-Top each with 1/2 of the mushroom mixture and finally the remaining slices of bread with the buttered side up.
-Grill until the cheese has melted and the bread is golden brown, about 2-4 minutes per side.