Preheat your oven to 180°C (350°F). Roll out the chilled pie crust on a floured surface to about ¼ inch thickness and fit it into your 9-inch pie dish. Prick the bottom with a fork to prevent bubbles.
Line the crust with parchment paper and fill with pie weights or dried beans. Bake for 15 minutes until the edges are just beginning to turn golden. Remove from oven, lift out the weights and parchment, then bake for another 5 minutes until the crust is lightly crisp.
While the crust bakes, trim the asparagus spears and toss them with a little olive oil, salt, and pepper. Roast on a baking sheet for about 10–12 minutes until slightly caramelized and tender. Let cool slightly.
Wash the spinach thoroughly, then wilt it quickly in a hot skillet until just tender, about 1–2 minutes. Drain any excess moisture and chop coarsely. Set aside.
In a large mixing bowl, whisk the eggs until frothy and slightly bubbly. Pour in the heavy cream and add a pinch of salt, pepper, and freshly grated nutmeg. Whisk until smooth and well combined.
Chop the roasted asparagus into 2-inch pieces and add them to the egg mixture along with the chopped spinach. Stir in the grated Gruyère cheese until evenly distributed.
Pour the filling into the pre-baked crust, spreading it evenly with a spatula. Place the pie dish on a baking sheet to catch any spills.
Bake the quiche for 30–35 minutes, or until the edges are golden and the center is just set with a slight jiggle. The top should be lightly browned and fragrant.
Remove the quiche from the oven and let it rest on a wire rack for about 10 minutes. This helps it set and makes slicing easier.
Slice the quiche into wedges with a sharp knife, serving warm or at room temperature. Garnish with extra cheese or herbs if desired.
