In a large pot, melt the butter and add the onion. Cover with aluminum foil and the pot lid, and cook on low heat for 50 minutes or until the onion is very soft and somewhat caramelized.
Remove the lid and aluminum foil, and add the sugar to the onion. Cook on high heat, stirring continuously until the onion is well caramelized and light brown in color.
Season with salt and pepper and add the beef broth. Cook for 10 minutes.
While the soup is cooking, cut the baguette into pieces and toast them.
To assemble the soups, place 6 deep bowls (that can later go in the oven) and divide the soup among the 6. Place 2 pieces of bread on top of each soup and a handful of shredded Gruyere cheese.
Place the bowls on a tray and cook under the broiler for 10 minutes or until the cheese is melted and slightly golden.
Nutritional Information
* * Information per 100g serving, percentage of daily values based on a 2,000 calorie diet.
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