Preheat the oven to 400°F (200°C). Place the rack in the lowest position.

Dock the bottom of the frozen pie shell with a fork.

Place the pie shell on a baking sheet.

Bake the pie shell for 12-14 minutes, or until slightly puffed.

Remove from the oven and set aside.

Reduce the oven temperature to 350°F (175°C).

Heat olive oil in a large skillet over medium-high heat.

Add spinach to the skillet and cook until wilted (about 1 minute).

Remove the skillet from the heat and set aside.

In a large mixing bowl, whisk together eggs, milk, heavy cream, salt, and pepper.

Combine spinach, mozzarella, and parmesan cheese into the egg mixture.

Fold gently to evenly distribute the ingredients.

Pour the mixture into the pre-baked pie shell.

Cover the edges of the pie shell with pie guards or aluminum foil.

Bake the quiche for 45-55 minutes, or until the top is firm and golden brown.

Check for doneness; add baking time if needed.

Allow the quiche to cool for at least 30 minutes before slicing and serving.

Store leftovers covered in the refrigerator for up to 3 days.