penne con cheddar

Ingredients

• 1/4 cup (1/2 stick) butter
• 5 cups chopped leeks (white and pale green parts only; about 5 large)
• 1/4 cup all purpose flour
• 3 1/2 cups whole milk
• 1 pound extra-sharp cheddar cheese, coarsely grated (about 4 cups packed)
• 1 tablespoon Dijon mustard
• 1 teaspoon hot pepper sauce
• 2 large eggs
• 1 pound penne pasta

Preparation

• Lightly butter 15x10x2-inch baking dish. Melt 1/4 cup butter in heavy large saucepan over medium heat. Add leeks; stir to coat. Cover saucepan and cook until leeks are tender, stirring occasionally, about 12 minutes (do not brown). Uncover saucepan; add flour. Stir 2 minutes. Add milk; bring to simmer, stirring often. Add cheese, mustard, and pepper sauce. Stir until cheese melts. Remove from heat. Season cheese sauce to taste with salt.
• Whisk eggs in medium bowl. Gradually whisk in 1 cup cheese sauce. Stir egg mixture into cheese sauce in saucepan.
• Meanwhile, cook pasta in large pot of boiling salted water until just tender but still firm to bite, stirring occasionally. Drain. Return to pot.
• Stir cheese sauce into pasta in pot. Transfer to prepared baking dish. DO AHEAD Can be made 2 hours ahead. Let stand at room temperature.
• Preheat oven to 400°F. Bake pasta until cheese sauce is bubbling around edges and some ends of pasta are golden brown, 25 to 30 minutes.
• Let stand 15 minutes. Serve hot 
• Unlike classic mac and cheese, which is thickened by a roux (a flour and butter mixture), this one uses eggs to make a rich, gooey custard. But be careful when adding the hot cheese sauce to the eggs; you'll need to whisk the sauce in slowly so that the eggs don't curdle.