You can skip the whiskey, all together, or use a dry sherry if you prefer.
You may be able to use less butter in your dutch oven as well, using a single stick, if you have a smaller dutch oven.
If you don’t have croutons, you can top with toasted bread, cut to fit the bowls as well.
If you don’t have Gruyère cheese, you can use Havarti, Parmesan, or Mozzarella, or a mix. Smoked Havarti adds an interesting flavour to the finished soup.