Crispy-Creamy Sheet-Pan Macaroni and Cheese

Steps

1. 1Adjust oven racks to upper-middle and lower-middle positions and heat oven to 400 degrees. Combine 1 pound elbow macaroni with 4 cups boiling water in large bowl. Cover and let sit for 12 minutes, stirring occasionally.
2. 2Meanwhile, line rimmed baking sheet with parchment paper and sprinkle 1 cup shredded sharp cheddar cheese in center of sheet, spreading into rough 10 by 8‐inch rectangle. Bake on upper rack until cheese is browned and lacy, 8 to 12 minutes. Transfer sheet to wire rack and let cool slightly, then use spatula to slide crispy cheddar onto double layer of paper towels. Discard parchment, reserving sheet. Once cool enough to handle, break crispy cheddar into ½- to 1‐inch pieces; set aside.
3. 3Reserve ½ cup soaking water, then drain pasta and return it to bowl. Add 2 cups shredded American cheese, remaining 1 cup shredded sharp cheddar cheese, and reserved soaking water and stir vigorously until most of cheese is melted (some small clumps of cheese will remain; that is OK) and water has been absorbed. Stir in 1 (12‐ounce) can evaporated milk, ½ cup sour cream, 1¼ teaspoons table salt, and ½ teaspoon dry mustard until well combined.
4. 4Brush bottom and sides of now-empty sheet with 3 tablespoons melted unsalted butter. Transfer pasta mixture to sheet, being sure to scrape out any remaining cheese mixture in bowl, spreading into even layer if needed. Bake on lower rack until sauce is bubbling, 13 to 15 minutes.
5. 5Meanwhile, toss ¾ cup panko bread crumbs with remaining 1 tablespoon melted butter in bowl until evenly coated. Microwave, stirring frequently, until light golden brown, 2 to 4 minutes.
6. 6Remove sheet from oven and sprinkle crispy cheddar pieces and toasted panko evenly over top. Serve immediately.