Preheat the oven to 350°.
Arrange the pie pastry in a pie pan, pressing firmly on the bottom and sides of the pan. Fold any overhanging edges of the pastry under itself and using your fingers or the tines of a fork, press the edges to form a decorative rim. Refrigerate until ready to fill and bake.
Squeeze all the excess moisture from the thawed spinach. Set aside.
f you have a high-powered professional blender (like a Vitamix) place the eggs, half and half, nutmeg and spinach in the blender and turn on low, gradually increasing the speed until emulsified and bright green. Pour the mixture into a large bowl. Season with the salt and pepper and stir in 1 cup of the cheese. Transfer the spinach mixture to the pastry shell. Sprinkle with the remaining cheeses and bake for 40-45 minutes or until quiche is set. Let cool for 20 minutes before cutting.
To make the quiche without a blender
Finely chop the spinach. Whisk the eggs and half and half in a large bowl until well combined, then stir in the spinach, nutmeg, salt and pepper. Stir until well combined and proceed with the recipe. The processing power of a professional blender is what lends the bright green color to this quiche. Chopping the spinach by hand won't achieve the same look, but the flavor will be delicious.