Saute onions in the 3 tablespoons butter just until tender.
Stir in the flour and pepper until smooth and bubbly.
Add the broth and sherry.
Continue to cook, stirring, until thickened and bubbly.
Pour onion mixture into a 1 quart casserole.
Toss croutons with the 2 tablespoons butter and spoon
over top of the onion mixture.
Sprinkle with the Swiss and Parmesan cheeses.
Broil until the cheese is melted and lightly browned, about 1 minute.
Serve immediately. Makes 4 - 6 servings.