Steps
1. Preheat the oven to 375°F (190°C).
2. Place the pre-made pie crust into a 9-inch pie dish and set aside.
3. In a skillet, sauté the mushrooms over medium heat until they release their moisture and become tender. Remove from heat and set aside.
4. In the same skillet, wilt the fresh spinach until it is slightly wilted, then remove from heat.
5. In a bowl, whisk together the eggs, heavy cream, salt, and pepper.
6. Spread the sautéed mushrooms and wilted spinach evenly over the pie crust.
7. Sprinkle the shredded Gruyere cheese over the vegetables.
8. Pour the egg and cream mixture over the vegetables and cheese.
9. Bake in the preheated oven for 30-35 minutes, or until the quiche is set and lightly golden on top.
10. Remove from the oven and let it cool for a few minutes before serving.