Deep-Dish Quiche Lorraine

1. FOR THE CRUST: Process flour and salt together in food processor until combined, about 3 seconds. Add butter and pulse until butter is size of large peas, about 10 pulses.
2. Combine sour cream and 1⁄4 cup ice water in small bowl. Add half of sour cream mixture to flour mixture; pulse 3 times. Repeat with remaining sour cream mixture. Pinch dough with fingers; if dough is floury, dry, and does not hold together, add 1 to 2 tablespoons more ice water and pulse until dough forms large clumps and no dry flour remains, 3 to 5 pulses.
3. Turn dough out onto counter and flatten into 6-inch disk; wrap disk in plastic wrap and refrigerate until firm but not hard, 1 to 2 hours, before rolling. (Dough can be refrigerated for up to 1 day; let stand at room temperature for 15 minutes before rolling.)
4. Cut two 16-inch lengths of aluminum foil. Arrange foil pieces, perpendicular to each other, in 9-inch round cake pan, pushing them into corners and up sides of pan; press overhang against outside of pan. Spray foil lightly with vegetable oil spray.
5. Roll out dough on generously floured counter to 15-inch circle about 1⁄4 inch thick. Roll dough loosely around rolling pin and unroll into prepared cake pan. Working around circumference, ease dough into pan by gently lifting edge of dough with 1 hand while pressing into pan bottom with other. Trim any dough that extends more than 1 inch over edge of pan. Patch any cracks or holes with dough scraps as needed. Refrigerate any remaining dough scraps. Refrigerate dough-lined pan until dough is firm, about 30 minutes, then freeze for 20 minutes.
6. Adjust oven rack to lower-middle position and heat oven to 375 degrees. Line dough with foil or parchment paper and fill completely with pie weights, gently pressing weights into corners of shell. Bake on rimmed baking sheet until exposed edges of dough are beginning to brown but bottom is still light in color, 30 to 40 minutes. Carefully remove foil and pie weights. If any new holes or cracks have formed in dough, patch with reserved scraps. Return shell to oven and bake until bottom is golden brown, 15 to 20 minutes longer. Remove shell from oven and brush interior with egg white. Set aside while preparing filling. Reduce oven temperature to 350 degrees.
7. FOR THE CUSTARD FILLING: Cook bacon in 12-inch skillet over medium heat until crisp, 5 to 7 minutes. Transfer to paper towel–lined plate and discard all but 2 tablespoons bacon fat from skillet. Return to medium heat, add onions, and cook, stirring frequently, until softened and lightly browned, about 12 minutes. Set aside to cool slightly.
8. Whisk cornstarch and 3 tablespoons milk together in large bowl to dissolve cornstarch. Whisk in remaining milk, eggs, egg yolk, cream, salt, pepper, nutmeg, and cayenne until smooth.
9. Scatter onions, bacon, and cheese evenly over crust. Gently pour custard mixture over filling. Using fork, push filling ingredients down into custard and drag gently through custard to dislodge air bubbles. Gently tap pan on counter to dislodge any remaining air bubbles.
10. Bake until top of quiche is lightly browned, toothpick inserted in center comes out clean, and center registers 170 degrees, 1-1⁄4 to 1-1⁄2 hours. Transfer to wire rack and let stand until cool to touch, about 2 hours.
11. When ready to serve, use sharp paring knife to remove any crust that extends beyond edge of pan. Lift foil overhang from sides of pan and remove quiche from pan; gently slide thin-bladed spatula between quiche and foil to loosen, then slide quiche onto serving plate. Cut into wedges. Serve warm or at room temperature.

DEEP-DISH QUICHE WITH LEEKS AND BLUE CHEESE
Sweet leeks and tangy blue cheese make perfect partners in this variation.
Omit bacon and onions. Melt 1 tablespoon unsalted butter in 12-inch skillet over medium heat. Add 4 large leeks, white and light green parts only, halved lengthwise, sliced 1⁄4 inch thick, and washed thoroughly; cook until softened, 10 to 12 minutes. Increase heat to medium-high; continue to cook, stirring constantly, until leeks are beginning to brown, about 5 minutes. Transfer leeks to plate lined with triple layer of paper towels; press with double layer of paper towels to remove excess moisture. Increase salt in filling to 1 teaspoon. Substitute 6 ounces crumbled blue cheese for Gruyère; scatter blue cheese and sautéed leeks evenly over crust before adding custard. Reduce baking time to 1 to 1-1⁄4 hours.

DEEP-DISH QUICHE WITH SAUSAGE, BROCCOLI RABE, AND MOZZARELLA
Be sure to use supermarket-style low-moisture mozzarella in this variation; fresh mozzarella will make for a too-wet filling.
Omit bacon and onions. Cook 8 ounces hot or sweet Italian sausage, casings removed, in 12-inch skillet over medium heat, breaking sausage into 1⁄2-inch pieces, until no longer pink, 5 to 7 minutes. Transfer to paper towel–lined plate and discard all but 2 tablespoons fat from skillet. Return skillet to medium heat, add 8 ounces broccoli rabe, trimmed and cut into 1⁄2-inch pieces, and cook until slightly softened, about 6 minutes. Transfer rabe to plate lined with triple layer of paper towels; press with double layer of paper towels to remove excess moisture. Increase salt in filling to 1 teaspoon. Substitute 6 ounces shredded low-moisture whole-milk mozzarella cheese for Gruyère; scatter mozzarella, cooked sausage, and broccoli rabe evenly over crust before adding custard. Reduce baking time to 1 to 1-1⁄4 hours.