No one will believe that you made this French Onion Soup at home, it's that good. It's really simple to make since the slow cooker does all of the work. Make it on a day when you have a lot of time, because even though it is simple to do, it isn't quick.
3 lb. sweet onions, thinly sliced
4 T. unsalted butter, melted
2 t. brown sugar
1 t. salt
2 t. sherry vinegar
1 T. Worcestershire sauce
5 fresh thyme sprigs
3 bay leaves
6 c. beef stock
Kosher salt, to taste
freshly ground black pepper, to taste
12 oz. French baguette, sliced
2 c. Gruyère cheese, shredded
Add the thinly sliced onions to a 6 quart slow cooker. Stir in butter, brown sugar, 1 t. salt, sherry vinegar and Worcestershire sauce. Cover; cook on High 8-9 hours or on Low for 12-14 hours or until onions are caramelized and browned, stirring halfway through, as needed, to prevent burning.
Stir in beef stock, season, to taste with salt and pepper; add thyme sprigs and bay leaves. Cover; cook on High 2-3 hours or on Low 4-5 hours. When done, discard thyme and bay leaves.
Preheat oven to broil.
Place baguette slices on a baking sheet; broil until golden brown on both sides, about 1-2 minutes per side.
Place ovenproof bowls on a baking sheet; ladle soup into the bowls; top each bowl with 2 toasted baguette slices, the bread should cover the soup; top with lots of Gruyère shredded cheese.
Broil in the oven until the cheese is bubbly and golden brown, about 2 minutes.
Serve immediately.
8 servings.