Step 1

Place onions into a 6-qt slow cooker.

Step 2

Stir in butter, brown sugar and 1 teaspoon salt; top with thyme and bay leaf. Cover and cook on high heat for 8-10 hours, or until onions are caramelized and browned.*

Step 3

Stir in beef stock and sherry; season with salt and pepper, to taste. Cover and cook on high heat for 2-3 hours, or until heated through. Remove and discard thyme and bay leaf.

Step 4

Preheat oven to broil.

Step 5

Place baguette slices onto a baking sheet. Place into oven and broil until golden brown on both sides, about 1-2 minutes per side; set aside.

Step 6

Divide soup into ramekins or ovenproof bowls. Place onto a baking sheet. Top with baguette slices to cover the surface of the soup completely; sprinkle with cheeses. Place into oven and broil until golden brown and cheeses have melted; about 2 minutes.

Step 7

Serve immediately.