A rich soup perfect for these cool days. Serve with a green salad or roasted winter veggies and toasted French bread for a delicious and hearty meal.
Melt butter with olive oil in an 8 quart stock pot on medium heat. Add onions and continually stir until tender and translucent. Do not brown the onions.
Add beef broth, sherry and thyme. Season with salt and pepper, and simmer for 30 minutes.
Heat the oven broiler.
Ladle soup into oven safe serving bowls. Place bowls on cookie sheet and broil in the preheated oven until cheese bubbles and browns slightly.