For a richer flavor, consider using heavy cream instead of whipping cream. If you don't have Gruyere cheese, you can substitute with another flavorful cheese like Comté or Emmental. To prevent the top from browning too quickly, you can loosely tent the gratin with foil during the last 15 minutes of baking. A mandoline slicer can be helpful for achieving uniformly thin slices of carrots and potatoes.