If you are making the crust from scratch, you will make that first. If using a pre-made pie crust, jump below to step 7.
To make the crust, add the flour, salt and sugar into a food processor and pulse a couple of times. Place the shredding disc (grating disc) on the food processor and feed the butter through the feed tube on the lid to shred the butter into the flour.
Dump this mixture into a large cutting board and work in butter with your fingers. Gradually drizzle 1/4 cup ice water into the dough and begin to incorporate it into the dough. Fold and form the dough gently. Knead dough until somewhat smooth. Don’t over work the dough, you won’t get flakey pie crust that way. Wrap your dough in plastic wrap and chill in the fridge for 2 hours.
Once chilled, roll out the dough on a lightly floured surface using a rolling pin to a 14" round. Transfer the dough to a 9" pie pan/ pie plate. Trim away any overhang and reserve any scraps for patching.
Decorate the pie crust edge either with a fork or you can make a ruffle edge by using the thumb and forefinger of one hand and pulling gently with the forefinger of the other hand.
Freeze dough for 30 minutes. Then, line dough with 2 layers of overlapping parchment paper and fill with pie weight or if you don't have those you can always use dried beans. Bake in the oven at 350°F for 20 minutes and then remove pie weights and parchment paper and bake for 10-15 minutes just until crust begins to brown. Let this cool while you make the filling.
Sauté the spinach in a frying pan on the stove over medium heat until cooked down. Set aside to cool.
Whisk together the eggs, both cheeses, and heavy cream. Then add in spinach and mix again. Sprinkle 1/4 cup cheese down onto the crust, followed by the filling and then top with more white cheddar to finish. Bake for 40-45 minutes at 350°F or until the edges are set but it still jiggles just a little in the center of the quiche.
Cool the quiche for at least 20 minutes, but I always let it rest overnight in the refrigerator to let it set up completely. It's too delicate and fragile right out of the oven to slice into it right away. Ideally you want the quiche to cool in the pan before serving! Enjoy cold, room temperature or warmed.