Unroll both pie doughs on a lightly floured surface. Brush 1 pie dough lightly with 1 1/2 teaspoons water. Place remaining pie dough on top, rolling to a 15-inch circle.
Using a sharp knife, trim dough to a 12-inch circle, discarding the trimmings or rolling for another use.
Transfer dough to a 10-inch quiche dish, pressing in the bottom and up the sides, folding the excess dough into the sides of the dish. Lightly press and crimp the edges around the dish.
Using a fork, pierce the bottom of the dough. Place in the freezer for 10 minutes.
Arrange an oven rack on the lowest part of the oven and preheat to 375 degrees F. Line the pie crust with parchment paper, filling with pie weights.
Place into oven and bake for 5 minutes; let stand 5-10 minutes before removing pie weights and parchment paper.
In a large bowl, whisk together eggs, half and half, flour, Dijon, 1 teaspoon salt and 1/2 teaspoon pepper.
Heat a large cast iron skillet over medium high heat. Add bacon and cook until brown and crispy, about 6-8 minutes. Drain excess fat, reserving 1 tablespoon in the skillet; transfer bacon to a paper towel-lined plate.
Working in batches, add spinach, and cook, stirring occasionally, until wilted and excess liquid has evaporated, about 5 minutes. Stir in green onions; remove from heat.
Stir in bacon; season with salt and pepper, to taste. Let cool 5-10 minutes.
Add spinach mixture evenly into the pie crust; sprinkle with cheese.
Pour egg mixture into the pie crust.
Place into oven and bake until the crust is golden brown, and the center is almost set and jiggling slightly, about 40-45 minutes.
Let stand 10 minutes before slicing. Serve warm, at room temperature or cold.
Notes
Use a different cheese. Gruyere is a quintessential choice for quiche but Swiss, cheddar, Monterey Jack and fontina are all great alternatives. Avoid wet cheeses such as mozzarella as it can lead to a soggy quiche.
Bake on the bottom rack. This will ensure that the pie crust will get crisp and golden-brown throughout, preventing that dreaded soggy bottom.
Foil the crust. If the crust browns too quickly, cover loosely with foil.
Let the quiche cool. This allows the quiche to fully set and firm up, letting the residual heat finish cooking the quiche and allowing for clean slices.
Bake until the center still jiggles a little. You want a slight wobble in the center of the quiche, similar to Jello.
Make ahead of time. The crust can be blind baked up to 2 days ahead of time (covered tightly and stored at room temperature) or the quiche can be assembled and baked up to 2 days in advance (stored in the fridge), and can be served at room temperature or warmed at 300°F.