French Onion Soup

**For the broth:** - 3 beef shins, split in half - 1 large yellow onion, roughly chopped - 2 red onion, roughly chopped - 4 celery stalks, roughly chopped - 3 carrots, roughly chopped - 1 leek, roughly chopped **For the soup:** - 5 yellow onions, thinly sliced - 50g butter - 3 tbsp whisky - 1 tbsp all-purpose flour - The prepared broth - 1 sprig rosemary - 2 sprigs thyme - 2 bay leaves - Salt an