This 30-minute mac and cheese from chef Ashley Christensen is a bestseller at her Raleigh, NC restaurant, Poole's Diner. What makes it special: the three-cheese combo is brûléed under the broiler for a crust you must crack through to reach the creamy macaroni below.
Preheat broiler. In a medium saucepan over high heat, bring 2 quarts water and kosher salt to a boil. Add macaroni and return water to a boil; cook until barely al dente, about 5 minutes. Meanwhile, in a large bowl, stir the grated Grana Padano, Jarlsberg, and Cheddar cheeses to combine. Set aside. Taste a macaroni for doneness: it should be chewy yet firm. Strain macaroni in a colander and set aside.
Add heavy cream and a pinch of sea salt to an oven-safe skillet; turn heat to medium-high and bring to a simmer. When cream is simmering, fold in the macaroni. Continue to simmer to reduce and thicken, about 1½–2 minutes. Stir in ¼ of the cheese mixture to combine with noodles. Turn off the heat and stir in another ¼ of the cheese. Place remaining cheese over the top in an even layer (do not stir).
Set rack in the oven about 4 inches from the broiler. Place skillet under the broiler until cheese melts and caramelizes into a golden brown crust, 3–5 minutes (keeping an eye on it so it doesn’t burn). Remove gratin from oven and let rest 5 minutes before serving.