01 -
In a skillet, melt butter with olive oil over medium heat. Add sliced mushrooms, minced garlic, salt, and black pepper. Cook until mushrooms are tender and golden, about 5-7 minutes.
02 -
Spread mayonnaise evenly on the bread slices if using. Place Swiss cheese slices on one side of each bread slice, then top with the sautéed mushroom mixture.
03 -
Place the assembled sandwiches in the skillet over medium heat. Cook until the cheese melts and the bread turns golden brown on both sides, approximately 5-7 minutes, flipping carefully.
04 -
Remove sandwiches from the skillet, garnish with fresh parsley, and serve immediately while hot.