In a large skillet, heat the bacon, onion, and mushrooms. Cook on medium high for about 15 minutes until the bacon starts to brown, the onions are clear, and the mushrooms are tender. Stir in the fresh herbs. Season to taste with salt and pepper.
Heat a panini press or griddle.
If using a griddle, butter one side of each slice of bread.
Assemble sandwiches, butter side out, by layering cheese and bacon mixture between two slices of bread.
Cook in press or on griddle until toasted on both sides and cheese is melted.
Nutritional values are approximate and are based on 1/4 of the recipe. Refrigerate leftovers promptly and use within 4 days.