Optional to serve
- Sauté onions. Melt the butter in a large 28cm, wide heavy-based saucepan over medium heat, add onions, cover and cook, stirring occasionally, for 20 minutes or until onions are soft.
- Reduce onions. Remove lid and cook for 1 hour, stirring occasionally, scraping the base of pan to loosen any caramelised bits or until soft and starting to caramelise.
- Add stock. Add 1 cup of stock, and simmer for 5 minutes or until stock has almost evaporated.
- Add herbs. Using kitchen string, tie herbs together, add to onions with remaining 3 cups of stock and season to taste with sea salt and freshly ground black pepper.
- Bring to a simmer, scraping the base of pan, for 5 minutes or until thick.
- Make toasts. Preheat oven to 200C. Place the bread slices on a baking paper-lined oven tray and toast under the grill until golden. Scatter with cheese and grill until cheese is golden.
- Optional to serve. Remove herb bundle. Add 100g chopped butter and using a stick blender, puree the top layer of soup to make a creamier soup.
- Serve it up. Ladle soup into bowls and top with baguette. Then place on oven tray and grill to warm through the cheese again. Serve immediately.