Deep-Dish Quiche with Leeks and Blue Cheese | America's Test Kitchen

Ingredients

• 1 3/4 cups (8¾ ounces/248 grams) unbleached all-purpose flour , plus more for work surface
• 1/2 teaspoon table salt
• 12 tablespoons unsalted butter (1 1/2 sticks), cold, cut into 1/2-inch cubes and frozen 10 minutes
• 3 tablespoons sour cream
• 1/4-1/3 cup ice water
• 1 large egg white , lightly beaten
• 1 tablespoon unsalted butter
• 4 large leeks , white and light green parts halved lengthwise, washed, and sliced 1/4 inch thick
• 1 1/2 tablespoons cornstarch
• 1 1/2 cups whole milk
• 8 large eggs
• 1 large egg yolk
• 1 1/2 cups heavy cream
• 1 teaspoon table salt
• 1/4 teaspoon ground black pepper
• 1/8 teaspoon grated nutmeg
• 1/8 teaspoon cayenne pepper
• 6 ounces (170 grams) Roquefort cheese or other blue cheese, crumbled (about 1 1/2 cups)