Bring a large pot of salted water to a boil. Cook the macaroni pasta according to the package instructions until al dente. Drain and set aside.
Cook the lobster tails in boiling water for about 8-10 minutes until the shells turn bright red and the meat is cooked through. Remove from water, allow them to cool, then remove the meat from the shells and chop into bite-sized pieces.
In a large skillet over medium heat, melt the butter. Once melted, sprinkle in the flour and whisk constantly until smooth and bubbly, about 1-2 minutes.
Gradually pour in the milk while whisking continuously to prevent lumps from forming. Cook the mixture for another 2-3 minutes until it thickens slightly.
Stir in the shredded cheddar and Gruyere cheese until fully melted and the sauce is smooth. Season with salt and pepper to taste.
Add the cooked pasta and chopped lobster to the cheese sauce in the skillet. Stir until everything is evenly coated with the cheese sauce.
If desired, you can transfer the skillet to a preheated oven and bake at 350°F (175°C) for about 10-15 minutes until the top is golden and bubbly.
Once baked (if applicable), remove the skillet from the oven and let it cool for a few minutes before serving. Garnish with chopped parsley or chives if desired, and enjoy your delicious skillet lobster mac and cheese!