Peel the onions, quarter them and cut them into strips. Heat the butter and sauté the onions for 5 minutes until translucent. Extinguish with clear soup and cook for 10 minutes. Add wine, season with pepper, salt and sugar and simmer for 5 minutes.
Drizzle baguette slices with a little oil and toast in frying pan until completely dry. Divide soup evenly among 4 cups, place three baguette slices on each and sprinkle with cheese.
Bake in a heated oven at 220 degrees for about 10 minutes.
In France, onion soup is usually baked with Gruyére cheese. The stock is beef broth with carrots, celery and leek as well as cloves and black pepper.
Tip: Do you know purple carrots? This is an old, very aromatic variety – why not use it for a change!