Caramelize the onions

• Heat the olive oil and butter in a large pot over medium heat.
• Add the sliced onions and season with salt and pepper.
• Cook until deeply caramelized, stirring occasionally at first then more frequently toward the end so they don't burn.

Add garlic and flour

• Add the minced garlic and cook for 1–2 minutes.
• Sprinkle in the flour and stir well.
• Cook for another minute to get rid of the raw flour taste.

Deglaze with wine

• Pour in the white wine and scrape the bottom of the pot to loosen all the caramelized bits.

Build the soup

• Add the beef stock, Worcestershire sauce, garlic powder, parsley, oregano, thyme and bay leaves.
• Stir everything together and bring to a simmer.

Simmer the soup

• Reduce the heat to medium-low and let the soup simmer so all the flavors come together.

Toast the baguette

• Preheat the oven to 200 °C (400 °F).
• Slice the baguette and arrange the pieces on a baking sheet.
• Toast until golden around the edges.

Season the soup

• Remove the bay leaves.
• Taste the soup and adjust the salt and pepper if needed.

Top and broil

• Ladle the hot soup into oven-safe bowls and top each with a toasted baguette slice.
• Add a generous amount of mozzarella and Parmesan.
• Place the bowls on a baking sheet and broil until the cheese is melted, bubbly and golden, keeping a close eye on them so it doesn't burn.

Serve

• Serve immediately while the soup is hot and the cheese is perfectly melted.