Caramelize the Onions
In a large Dutch oven, melt the butter over medium-high heat. Add the sliced onions and cook, stirring occasionally, until softened, about 10 minutes.
Gradually pour in the apple cider, ¼ cup at a time, allowing it to cook into the onions before adding more. Repeat until all cider is used, and the onions are deeply golden (approximately 20 minutes).
Build the Flavor Base
Stir in the garlic, thyme, and sage, and season with salt and pepper. Cook for 3-4 minutes until fragrant.
Add the wine, broth, Worcestershire sauce (if using), and Parmesan rind. Increase heat to medium-high, bring the soup to a simmer, and cook for 10 minutes.
Stir in the cream or milk and simmer for an additional 5 minutes. Remove and discard the Parmesan rind. Adjust seasoning with salt and pepper to taste.
Prepare the Bread Bowls
Preheat your oven to 400°F (200°C). Arrange the hollowed-out bread bowls on a baking sheet and toast for 10 minutes.
Assemble and Bake
Ladle the hot soup into the toasted bread bowls. Top with Gruyère slices, covering the soup completely. Bake in the oven for 10 minutes, or until the cheese is bubbly and golden.
Serve and Garnish
Garnish with fresh thyme or crispy sage browned in butter for an extra touch of flavor. Serve immediately and enjoy!
