Preheat the oven to 350 degrees . Prick the crust all over with a fork, fill with pie weights and cover with foil. Bake for 15 minutes; remove the foil and weights.
In a small bowl, beat the egg white; lightly brush the crust with some egg white, reserving the rest. Bake until lightly golden, about 10 minutes. Let cool on a rack.
Meanwhile, add the leeks to a salad spinner and cover with water. Swish the leeks around to separate the pieces and dislodge any dirt. Slowly lift the basket from its bowl so the dirt stays at the bottom; discard the water and rinse the bowl. Replace the basket and spin the leeks dry.
In a medium skillet, cook the bacon over medium heat until lightly golden, 8 to 10 minutes. Drain off all but about 1 tablespoon bacon grease. Add the leeks to the skillet and cook until crisp-tender, about 2 minutes. Let cool.
In a large bowl, beat together the remaining whole egg, egg yolk, beaten egg white and the sour cream. Stir in the heavy cream, milk, nutmeg, 1/4 teaspoon salt and 1/4 teaspoon pepper. Set the crust on a baking sheet. Spread the leek-bacon mixture in the bottom, then pour in the cream mixture. Bake until set, about 35 minutes. Transfer to a rack to cool for 20 minutes before serving.