Preheat your oven to 350°F (175°C).

In a large bowl, combine the ground beef, breadcrumbs, Parmesan cheese, egg, minced garlic, salt, black pepper, and dried oregano. Mix until just combined, then form into small meatballs, about 1 inch in diameter.

In the large pot or Dutch oven, melt butter over medium heat. Add sliced onions and cook, stirring frequently. After about 15 minutes, sprinkle the sugar over the onions to help with caramelization. Continue to cook for about another 20 minutes until the onions are a deep golden brown and soft.

Add the white wine to the onions and scrape any browned bits off the bottom of the pot. Allow it to simmer for 2-3 minutes.

Pour in the beef broth and water, then add thyme. Season with salt and pepper to taste. Bring to a boil.

Once boiling, reduce heat to a simmer. Gently add the meatballs to the soup and cook for about 20 minutes or until the meatballs are cooked through.

While the soup is simmering, place the baguette slices on a baking sheet and toast them in the oven for about 5-7 minutes or until slightly golden.

To serve, ladle the soup into oven-safe bowls or ramekins. Float a toasted baguette slice on top and sprinkle generously with Gruyere cheese.

Place the bowls on a baking sheet and broil in the oven for 2-3 minutes or until the cheese is bubbly and golden brown. Keep a close eye to prevent burning.

Serve immediately and enjoy your comforting French Onion Soup with Meatballs!