Yes, you can, and it will still be just as delicious. Instead of beef stock, use a vegetable stock cube or make your vegetable stock. Instead of dairy cheese, you can substitute vegan cheese. It comes in all sorts of flavors, including parmesan. You can freeze vegan French onion soup but again don’t freeze the baguette or vegan cheese in the soup. You can, however, freeze the baguette separately and it will last in the freezer for around three months, the same time as the soup.