Preheat oven to 400º F.

Wash large mushroom caps and pat dry. Remove the stems; include the stems in the 2 cups fresh mushrooms. Set mushroom caps aside.

By handfuls, twist the diced mushrooms in a paper towel to extract their juices. Repeat if necessary. Heat butter to bubbling in a large skillet. Sauté the mushrooms in hot butter over moderately high heat until the pieces begin to separate from each other - 3 to 4 minutes. Add the scallions and sauté a moment longer. Add the Madeira or port, letting it boil down to nothing. Season to taste with salt and pepper. Place mushroom mixture in a small bowl; add bread crumbs and sour cream. Mix thoroughly. Stuff the mushroom caps with the mushroom mixture. Place on a lightly greased baking pan with sides; top with grated Parmesan cheese and Swiss cheese. Bake for 20 minutes or until caps are browned and tender. Serve immediately. Yield: 4 servings.