CRUST 

In a food processor, combine flour, salt, and sugar; pulse to combine. Add butter and pulse until mixture resembles coarse meal with a few pea-size pieces of butter remaining. 

Sprinkle with ice water and egg yolk. Pulse until dough is crumbly but holds together when squeezed. 

Divide dough in half and flatten to disks (the dough may still be crumbly and hard to handle, but will rehydrate while resting), wrap each disk with parchment paper, and allow to rest in fridge for at least 1 hour and up to 2 days. Dough may also be frozen for up to 1 month. Preheat oven to 350°F. 

Place one disk of dough on a lightly floured piece of waxed paper. Rolling from center outward, form into a 14-inch round. Using paper, lift and wrap dough around a floured rolling pin; carefully unroll (discarding paper) over a 9-inch pie plate. 

Gently fit dough into bottom and sides of plate. Avoid stretching or tearing dough. Using kitchen shears, trim overhang to 1 inch; fold under to form a rim. Prick the dough all over the bottom and sides and a fork. Repeat with second disc of dough. 

Line the dough with foil and add pie weights, or beans or rice. Blind bake the dough for 15 minutes, until lightly browned. Remove foil and weights and continue to bake for another 10 minutes until the dough is dry. 

FILLING 

Melt butter in a large sauté pan over medium heat. Sweat shallots until translucent, about 3 minutes. Add garlic and spinach. Cook spinach for 3 minutes, stirring frequently, until wilted and soft. Drain spinach mixture in a colander by lightly pressing with a spatula to remove excess water. 

In a large mixing bowl, whisk together cheese, eggs, half-and-half, nutmeg, hot sauce, salt, and pepper. 

Arrange spinach in the bottom of blind-baked crust. Ladle custard over spinach. Sprinkle top with Parmesan cheese. Bake for 50 to 60 minutes or until top is puffed and golden. Serve at room temperature.