Bring a very large pot of water to a rolling boil. Add 2 tablespoons kosher salt. Add the elbow macaroni and cook until very al dente — about 1 to 2 minutes less than package directions (usually 6–7 minutes total). Reserve 1 cup of pasta cooking water, then drain the pasta and set aside.

Make roux

In a large heavy-bottomed saucepan over medium heat, melt 4 tablespoons unsalted butter. Add 4 tablespoons all-purpose flour and whisk continuously for 1 to 2 minutes until the raw flour smell is gone and the mixture is slightly nutty but not browned.

Make béchamel

Slowly whisk in 720 ml whole milk and 120 ml heavy cream in a steady stream to avoid lumps. Bring the mixture to a gentle simmer, whisking frequently, until it thickens enough to coat the back of a spoon (about 6–8 minutes). If the sauce becomes too thick, whisk in up to 1/2 cup of the reserved pasta water to loosen.

Season base

Stir in 1 teaspoon Dijon mustard, 1 teaspoon Worcestershire sauce, 1 teaspoon finely grated nutmeg, and 1 teaspoon freshly ground black pepper. Taste and adjust seasoning with the sea salt later after adding cheeses.

Cheeses & Truffle

Melt cheeses

Reduce heat to low. Remove the béchamel from direct heat and add the grated cheeses in three additions: 1/3 of the cheeses at a time, stirring gently until each addition melts fully into a smooth, glossy sauce. Avoid boiling once cheese is added to prevent graininess.

Add truffle oil

Once cheese is fully incorporated, stir in 2 teaspoons white truffle oil and the 8 g thinly sliced fresh black truffle if using. Taste and add the 1 teaspoon sea salt if needed. If the sauce feels too thick, whisk in up to the reserved pasta water by tablespoons until you reach a creamy consistency that evenly coats the pasta.

Combine with pasta

Add the drained al dente macaroni to the cheese sauce and gently fold until every piece is coated. If necessary, warm briefly over low heat while stirring — do not boil. The sauce should cling to the pasta, not pool heavily.

Topping (optional for bake)

Prepare topping

If you prefer a baked crust, preheat the oven to 180°C (350°F). In a small bowl combine 1 cup panko breadcrumbs, 2 tablespoons melted butter, 1 tablespoon minced parsley, and 2 tablespoons grated Parmesan. Toss to combine.

Assemble and bake

Transfer the mac & cheese to a lightly buttered 9x13-inch baking dish (or individual ramekins). Even the surface, sprinkle the breadcrumb mixture evenly over the top. Bake in the preheated oven for 15–20 minutes until the topping is golden and the edges are bubbly. For extra color, broil 1–2 minutes at the end — watch closely to avoid burning.

Finishing

Finish and serve

If not baking, simply garnish the skillet mac & cheese with a drizzle of the remaining 1 teaspoon extra truffle oil and a light dusting of extra Parmesan. If baked, remove from oven and let rest 5 minutes, then drizzle the finishing 1 teaspoon truffle oil over the top and sprinkle with a pinch of additional sea salt if desired. Serve immediately.