1. Begin by halving the onions, trimming the ends, then peeling and slicing them thinly, ensuring to cut parallel to the grain.
2. In a large, heavy-bottomed pot or Dutch oven set over medium heat, combine 2 Tbsp olive oil and 2 Tbsp butter. Introduce the sliced onions and sauté uncovered, stirring occasionally for about 10 minutes.
3. Sprinkle the onions with 1/2 tsp sugar to aid in caramelization. Continue to sauté uncovered for an additional 30-40 minutes, stirring occasionally until the onions are caramelized and browned. Increase stirring frequency towards the end to avoid scorching.
4. After the onions are caramelized, incorporate the minced garlic and sauté for another minute.
5. Pour in 1/2 cup apple juice and deglaze the pot by scraping the bottom. Keep stirring until the apple juice has completely evaporated, which should take around 3 minutes over medium heat.
6. Add 8 cups beef stock, 1 bay leaf, thyme, and 1 tsp salt. Partially cover the pot and let it simmer for 30 minutes to allow the flavors to meld. Adjust seasoning with an additional 1/2 tsp salt and 1/2 tsp black pepper, or to taste, then remove from heat.

How to Make Crouton Topping

1. While the soup is nearing completion, preheat the oven to 400˚F. Slice the baguette into 1/2” thick pieces. Lightly brush both sides with olive oil, arrange them on a baking sheet, and bake for 6-8 minutes until the edges are golden brown.
2. Once the soup is ready to serve, place half of the cheese on the toasts and broil for 2-3 minutes until the cheese melts and is golden in spots.
3. Serve the soup in warm bowls, sprinkling the remaining cheese over the hot soup. Top with the cheesy toasts and enjoy.