Bring a large pot of water to a rolling boil. Add 1 tablespoon kosher salt. Add the pasta and cook until just al dente according to package directions (usually 1–2 minutes less than package time). Reserve 1 cup of the pasta cooking water, then drain the pasta and set aside.

Prepare lobster and crayfish

If using pre-cooked lobster/crayfish, pat dry and roughly chop into 1/2" pieces. If using live lobster, steam or boil until just cooked through (about 8–10 minutes for a 1.25–1.5 lb lobster), cool slightly, remove meat from shell and chop. Gently toss the chopped lobster and crayfish with a pinch of fine sea salt and 1 teaspoon of melted butter (from the sauce butter allowance) and set aside at room temperature.

Three‑Cheese Sauce

Make a roux

In a medium saucepan over medium heat, melt 4 tablespoons unsalted butter. Add 4 tablespoons flour and whisk constantly for 1–2 minutes until the mixture is bubbly and smells slightly nutty but not browned.

Add milk & cream

Gradually whisk in 3 cups whole milk and 1 cup heavy cream, adding a little at a time to avoid lumps. Increase heat to medium-high and bring to a gentle simmer, whisking constantly, until the mixture thickens and coats the back of a spoon (about 4–6 minutes).

Season & melt cheeses

Reduce heat to low. Whisk in 1 teaspoon Dijon mustard, 1 teaspoon freshly grated nutmeg, 1 teaspoon Worcestershire sauce, 1 teaspoon sea salt and 1/2 teaspoon black pepper. Remove the pan from heat briefly and add the grated Gruyère, sharp white cheddar and fontina in small handfuls, stirring until each addition melts and the sauce becomes silky. If the sauce seems too thick, whisk in up to 1/2 cup reserved pasta water to reach a smooth, pourable consistency.

Finish sauce

Taste and adjust seasoning. Keep the sauce warm on the lowest heat, stirring occasionally to prevent skin from forming.

Crispy Panko & Shallot Crumb

Toast panko

In a small skillet over medium heat, melt 2 tablespoons butter. Add 1 cup panko breadcrumbs and cook, stirring frequently, until golden brown and crisp, about 4–6 minutes.

Add shallot & finish crumb

Stir in the minced shallot and cook for 1 minute until softened but not browned. Remove from heat and stir in 1 tablespoon chopped parsley, 1 teaspoon lemon zest and 1/4 teaspoon sea salt. Transfer to a bowl and set aside to stay crisp.

Assembly & Baking

Combine pasta, sauce & seafood

Preheat oven to 375°F (190°C). In a large mixing bowl or the pasta pot, combine the drained al dente pasta with the warm three-cheese sauce, folding gently to coat. Stir in the chopped lobster and crayfish, reserving 1–2 tablespoons of the seafood to garnish on top if desired. If the mixture seems tight, add 1/4–1/2 cup reserved pasta water to loosen.

Transfer & top

Transfer the mac & cheese mixture to a lightly buttered 9" x 9" baking dish (or equivalent). Evenly sprinkle the toasted panko & shallot crumb across the surface. Dot with a few small pieces of extra butter (optional) for browning.

Bake

Bake in the preheated oven until the topping is golden and the sauce is bubbling at the edges, about 18–22 minutes. For a crispier top, place under the broiler for 1–2 minutes—watch closely to avoid burning.

Finish with truffle dust & serve

Remove from oven and let rest 5 minutes. Lightly dust the surface with 1/2 teaspoon truffle powder and a final pinch (1/4 teaspoon) of fine sea salt and 1/4 teaspoon black pepper. Garnish with reserved lobster/crayfish pieces and chopped chives or microgreens. Serve hot.