Stovetop lobster macaroni and cheese combines tender lobster, Gruyère and mascarpone into a rich, creamy pasta dish that works as a special occasion side or elegant weekend dinner.
Bring a large pot of generously salted water to a boil. Reduce the heat to a steady simmer, add the lobster tails, and cook until the shells are bright red and the meat is opaque, 4 to 5 minutes. Use tongs to transfer to a plate and let cool.
Return the water to a boil. Add the cavatappi and cook until al dente according to package directions. Drain and set aside.
When the lobster tails are cool enough to handle, remove the meat from the shells and cut it into bite-sized chunks. To remove the meat easily, use kitchen shears to cut through the top shell, then gently pull the shell apart.
Warm the milk in a saucepan or microwave until hot but not simmering.
Melt the butter in a large, heavy saucepan over medium heat. Add the flour and whisk until smooth. Continue cooking, whisking constantly, until the mixture is pale golden, about 3 minutes.
Gradually whisk the warm milk into the flour mixture until smooth. Cook, whisking frequently, until the sauce thickens enough to coat the back of a spoon, 7 to 8 minutes. Season to taste with salt and pepper.
Reduce the heat to low and stir in the Gruyère until melted. Add the mascarpone and stir until smooth and creamy.
Add the cooked cavatappi, lobster meat, and chives. Stir gently until well combined. Remove from the heat and let stand for 5 minutes before serving.