Baked Penne with Farmhouse Cheddar and Leeks

1 pound penne
4 tablespoons (½ stick) unsalted butter, plus more for the baking dish
4 large leeks, white and pale green parts only, well rinsed, drained, and chopped (5 cups)
¼ cup flour
3½ cups whole milk, heated
4 cups (1 pound) shredded extra-sharp white Cheddar
1 tablespoon Dijon mustard
½ teaspoon hot red pepper sauce
Salt
2 large eggs

Leeks lift this macaroni and cheese out of the ordinary.

Preheat the oven to 400°F. Lightly butter a 15 x 10-inch baking dish.
Bring a large pot of salted water to a boil over high heat. Add the penne and cook, stirring occasionally, until barely tender (remember the pasta will be baked), about 8 minutes. Drain well.
Meanwhile, melt the butter in a large saucepan over medium heat. Add the leeks and cover. Cook, stirring occasionally, until the leeks are tender but not browned, about 10 minutes. Uncover and stir in the flour. Whisk in the milk. Bring to a simmer over medium heat, stirring often. Remove from the heat. Stir in the Cheddar, mustard, and red pepper sauce. Season with salt and additional red pepper sauce to taste.
Whisk the eggs in a medium bowl. Gradually whisk in about 1 cup of the hot cheese sauce, then stir the egg and cheese mixture back into the saucepan. Add the penne to the sauce and stir well. Spread in the baking dish.
Bake, uncovered, until the sauce is bubbling and the ends of the penne are tinged with brown, about 25 minutes. Serve hot.