You can definitely use Emmental cheese instead of gruyere cheese in your dish. Emmental has a slightly nutty flavor that would be a great addition to your dish. Gruyere, on the other hand, is a bit more earthy and pungent in flavor. So, it really depends on what you are looking for in terms of flavor. If you want a more subtle flavor, go with Emmental. If you're searching for something with a bit more depth of flavor, go with gruyere cheese. Either way, your dish will be delicious!