Begin by heating a skillet over medium heat. Add a splash of oil or a little butter, then toss in the sliced mushrooms. Sauté them until they are golden brown and tender, about 5-7 minutes. Season with salt and pepper to taste.

While the mushrooms are cooking, take two slices of your chosen bread and spread a generous layer of butter on one side of each slice. This will create that delightful, crispy crust when grilled.

On the unbuttered side of one slice, layer a slice of Swiss cheese, followed by the sautéed mushrooms, and then another slice of Swiss cheese. Top with the second slice of bread, buttered side facing out.

Place the sandwich in the skillet over medium heat. Cook for about 3-4 minutes on each side, or until the bread is golden brown and the cheese is beautifully melted. If necessary, lower the heat to ensure the cheese melts without burning the bread.

Once your Mushroom Swiss Breakfast Grilled Cheese is perfectly grilled, remove it from the skillet, slice it in half, and serve hot. Enjoy the gooey goodness!