Grilled Cheese with Gouda, Roasted Mushrooms, and Onions

In the melted butter, place one sandwich down for one second, then gently flip it over to the other side. Repeat with the other sandwich. Cook for about 2 minutes, until lightly browned, then gently flip the sandwich on the other side and cook for an additional 2-3 minutes, or until cheese is melted and the sandwich is browned to your preference