Step 1: Preheat your oven to 400°F (200°C). Toss the pumpkin cubes with olive oil and a pinch of salt on a baking sheet. Roast for 20 minutes or until tender and slightly caramelized.
Step 2: While pumpkin roasts, roll out the pie crust and fit it into a 9-inch tart pan. Line with parchment paper and pie weights, then blind bake at 375°F (190°C) for 12 minutes. Remove weights and bake for 5 more minutes.
Step 3: In a small skillet, sauté the garlic and baby spinach until wilted. Place the spinach in a clean kitchen towel and squeeze out all excess moisture. Rough chop the spinach.
Step 4: In a medium bowl, whisk together the eggs, heavy cream, whole milk, nutmeg, salt, and pepper until smooth but not frothy.
Step 5: Reduce oven temperature to 350°F (175°C). Layer the roasted pumpkin, chopped spinach, and shredded cheese into the pre-baked crust.
Step 6: Pour the egg mixture over the fillings, ensuring everything is evenly submerged. Gently tap the pan to remove any air pockets.
Step 7: Bake for 35-40 minutes, or until the edges are set and the center has a slight jiggle. Let the quiche rest for at least 15 minutes before slicing and serving.