Preheat oven to 350℉.
In a large skillet, melt butter over medium heat.
Add onions and saute until translucent.
Add a few turns of freshly ground pepper and stir.
Pour onions into a shallow 2-quart casserole dish.
Top with 2/3 of the Swiss cheese and set aside.
In a medium bowl mix soup, milk, and soy sauce. Pour over the cheese and onions.
Top with French bread slices.
Bake at 350℉, uncovered, for 15 minutes.
Remove from oven and gently push the bread down into sauce.
Top with remaining cheese.
Return to oven and bake, uncovered, for 15 minutes.
Serve immediately.
