Bring a large pot of water to a rolling boil. Add 1 tablespoon kosher salt. Add cavatappi and cook until al dente according to package directions (usually 8–10 minutes). Reserve 1 cup of pasta cooking water, then drain pasta and return to the pot. Toss with 1 tablespoon unsalted butter to prevent sticking and keep warm.

Prepare lobster

If using pre-cooked lobster meat, pat dry and chop into bite-size chunks. If using raw lobster tails, simmer or steam until opaque (about 6–8 minutes depending on size), cool slightly, remove meat from shell and chop. Gently fold lobster into the warm drained pasta just before combining with sauce, or keep separate and fold in after sauce step to avoid overcooking lobster.

House-made Cheese Sauce (Béchamel-based)

Make roux

In a medium heavy-bottomed saucepan over medium heat, melt 4 tablespoons unsalted butter. Once foaming but not browned, sprinkle in 1 tablespoon all-purpose flour and whisk constantly for 1–1½ minutes until mixture is fragrant and forms a smooth paste (roux). Do not let it brown.

Add milk & cream

Slowly add 2 cups warm whole milk and 1 cup warm heavy cream in a thin stream while whisking continuously to avoid lumps. Bring mixture to a gentle simmer over medium-low heat, stirring frequently, until it thickens slightly and coats the back of a spoon (about 6–8 minutes).

Season béchamel

Whisk in 1 teaspoon Dijon mustard, 1/2 teaspoon Worcestershire sauce, 1/8 teaspoon cayenne, 1/2 teaspoon freshly ground black pepper and 3/4 teaspoon kosher salt. Taste and adjust seasoning as needed.

Incorporate cheeses

Reduce heat to low. Remove saucepan from direct heat for 30 seconds to cool slightly (this prevents grainy cheese). Add 1½ cups sharp cheddar and 1 cup Gruyère a handful at a time, whisking until smooth before adding more. Finally whisk in 1/2 cup grated Parmesan until fully melted and sauce is glossy. If sauce is too thick, whisk in up to 1/2 cup reserved pasta water a few tablespoons at a time to reach desired consistency.

Combine & Bake

Combine pasta and sauce

Preheat oven to 375°F (190°C). In the pot with the drained pasta (or a large mixing bowl), pour the hot cheese sauce over the pasta and gently fold until all pasta is coated. If lobster was kept separate, fold in the chopped lobster now, reserving a small handful (about 2 tablespoons) for garnish.

Transfer to baking dish

Butter a 9x13-inch or similar baking dish lightly. Transfer the sauced pasta and lobster mixture to the dish, spreading evenly.

Make topping

In a small bowl, combine 3/4 cup panko breadcrumbs, 2 tablespoons melted butter, 2 tablespoons chopped parsley, 1 teaspoon lemon zest, 2 tablespoons grated Parmesan and 1/4 teaspoon smoked paprika (optional). Mix until crumbs are evenly coated.

Top and bake

Sprinkle the breadcrumb mixture evenly over the pasta. Bake in the preheated oven until the topping is golden and sauce is bubbling around the edges, about 20–25 minutes. For a crispier top, place under the broiler for 1–2 minutes—watch closely to prevent burning.

Finish & Serve

Remove the casserole from the oven and let rest for 5 minutes. Sprinkle reserved lobster pieces on top, scatter chopped chives, additional parsley if desired, and a light dusting of smoked paprika or extra Parmesan. Serve hot with lemon wedges on the side to squeeze over individual portions.