Simple French Onion Soup

1/2 c unsalted butter
2 tbsp olive oil
4 cups of sliced onions
4 cans beef broth
1 tsp dried thyme
salt and pepper to taste
4 slices french bread
4 slices provolone cheese
2 slices swiss cheese
1/4 c grated parmesan cheese

Melt butter with olive oil in an 8 quart stock pot on med-low heat. Gently sautee onions, stirring every few minutes. This will take 1 hour or more. The onions will eventually turn to a golden brown and they will increase in sweetness. This takes patience. DO NOT increase the heat because you don't want fried onions! The onions need to carmelize which happens at a lower temperature than frying.
Add broth and thyme. Season with salt and pepper and simmer for 1 hour.
Ladle soup onto oven safe serving bowls a place one slice of toasted bread on top of each. Layer each slice of bread with 1 slice of provolone, 1/2 slice of swiss and 1 tbsp of parmesan cheese. Place bowls on a cookie sheet and broil in oven until cheese bubbles.