This Roast Beef Mushroom Melt open-faced sandwich is loaded with flavorful ingredients: sour dough bread, deli roast beef, melted Havarti cheese, mushrooms and onions cooked in a delicious Marsala sauce and the topped off with peppery arugula.
Melt butter in a skillet over medium heat. Sauté onions and mushrooms until onions are translucent and mushrooms become glossy. Add marsala wine and deglaze pan by gently scraping the sides and bottom and stirring. Let bubble uncovered for about 5 minutes or until liquid has evaporated then remove from heat and set aside.
Top each slice of bread with roast beef then layer on a slice of Havarti cheese on each open-faced sandwich. You'll create 4 open-faced sandwiches total.
Layer mushrooms and onions on top of the cheese then toast the sandwiches in a toaster oven until cheese is melted and bread is golden brown. (You can toast in a conventional oven at 400˚for 4-6 minutes if you don't have a toaster oven)
Before serving, top with salt, fresh cracked pepper and finally arugula then serve warm.