Step 1

Preheat the oven to 350 degrees Fahrenheit. Melt the butter in a soup pot. Add onions, sugar, salt, dried thyme, and garlic powder. Sauté on medium-low heat for 30 minutes or until onions are golden brown. Make sure to stir them every 1-2 minutes to ensure that they don't burn. Towards the end of the 30 minutes, you can sir them less often. If the pot gets dry towards the end of caramelization, add an extra tablespoon of butter

Step 2

Add the flour and stir it into the onions. Next, deglaze the pan with white wine. As the white wine lifts the fond (brown bits) off of the bottom of the pot, scrape It up with your spatula

Step 3

Add the beef stock and a bay leaf. Bring the soup to a boil. Then, lower the heat to medium and allow to simmer with the lid partially off the pot for 20 minutes

Step 4

Place sliced baguettes onto a half sheet tray. Spray or lightly brush with olive oil and toast in the oven for about 14 minutes or until they're golden brown along the edges. Flip halfway through. Lower the oven to 300 degrees

Step 5

Ladle the soup into an oven-safe bowl or crock (or individual oven-safe bowls). Line top with sliced baguettes and mozzarella cheese. Put in the oven on the middle rack. Bake until the cheese melts, about 5 minutes