1. Cook the onions with the olive oil in a medium skillet over medium-low heat for
20 minutes, stirring occasionally, until golden brown and caramelized.
2. Meanwhile, melt the butter in a large skillet and sauté the mushrooms for 5
minutes, or until tender. Season with salt.
3. Preheat the broiler.
4. Form the beef into 8 4-ounce burgers. Season each burger with salt and pepper on
both sides. On a grill pan, cook the burgers on both sides to the desired doneness.
Transfer the burgers to a baking sheet and top each with a spoonful of the
mushrooms and a slice of the Comté cheese. Broil just until the cheese is melted.
5. Spoon some of the caramelized onions on the bottom of each bun. Place the
burger on top, followed by the top bun. Serve the mini burgers with lettuce and tomato on the side.