You will love this sweet and subtle red onion soup!
Peel the red onions and garlic. Then slice both roughly. Add half of the butter to a large saucepan together with the chopped garlic.
Place the pan over high heat until the butter has melt. Stir and cook the garlic for 3 minutes. Then add the sliced red onions and the fresh thyme sprigs.
Stir well and cook the onions for 3 minutes. Then pour in the warm stock. Season the onion soup with a dash of pepper.
Stir and bring it to a light simmer. Then put a lid on the pan and cook the soup for 5 minutes. After that pour in the balsamic vinegar. Also stir in the mustard.
Cook for 2 more minutes. Then check the seasoning and add extra pepper, salt, mustard or balsamic vinegar to taste. Take the pan off the heat and let it rest for now. Place the slices of French bread on a baking tray and top with the brie. Sprinkle with a little pepper and salt. Place the tray under a hot grill for 2 minutes or until the cheese has nicely melted. Remove the cheese toasts from the grill. Scoop the warm onion soup into bowls and top with the toast. Serve hot.