For an extra crispy crust, par-bake it with pie weights for the first 10 minutes. Feel free to experiment with different vegetables based on what's in season. Asparagus, zucchini, or even roasted sweet potatoes would be delicious additions. If you don't have Gruyere cheese, Swiss or Emmental cheese would work as great substitutes. Quiche can be stored in the refrigerator for up to 3 days. Reheat gently in the oven or microwave.