1/4  cup olive oil
3 tablespoons balsamic vinegar
 salt and freshly ground pepper
8  large Portobello mushrooms (6-8 ounces each)
1 slice Hautly Provolone cheese
2  ounces Hautly Asiago cheese, finely grated
2  teaspoons finely chopped fresh oregano (or 1/2 teaspoon dried)
4  slices tomato (1/4 inch thick)

Preheat the oven to 400°F.

     In a small bowl, whisk together the oil, vinegar and salt and pepper to taste. Set aside.
     Moisten a paper towel and wipe the mushrooms to remove dirt. Cut out the stems and the gills. Place mushrooms in a glass dish, round side up, and pour the oil mixture over them, rubbing it in with your fingers. Turn the mushrooms and lightly sprinkle the insides with salt and pepper. Marinate for 10 minutes.
     Remove the mushrooms from marinade and place on a baking sheet, rounded side up. Bake for 10 to 12 minutes, or until they begin to brown and shrink a bit. Turn the mushrooms and bake for 10 to 12 minutes, or until some of the liquid has surfaced and the mushrooms have browned further. Remove from the oven and let sit until cool enough to handle.
     In a small bowl, mix the asiago cheese and oregano. Distribute the cheese mixture evenly over the inside of 4 mushroom caps, followed by a slice of tomato and provolone. Sprinkle with salt and pepper to taste, and place the remaining 4 mushroom caps on top, rounded side up.
     Heat a large nonstick skillet over medium heat for 2 minutes. Put the mushrooms in the skillet (in batches if necessary), cover and cook for 3 to 5 minutes, or until the undersides are dark brown and the cheese had begun to melt. Uncover, and turn the mushrooms, pressing very firmly with a spatula to flatten them slightly. Cover and cook for 2 to 3 minutes or until the undersides have turned a shade or two darker and the cheese has melted completely. Let cool slightly, cut in half, and serve.