Begin by boiling a large pot of salted water. Add the elbow macaroni and cook according to the package instructions until al dente. Drain and set aside.
In a medium saucepan over medium heat, melt the unsalted butter. Once melted, whisk in the flour and cook for about 1 minute, stirring constantly until it forms a roux.
Gradually add the whole milk to the roux, whisking continuously to avoid lumps. Cook the mixture for about 5-7 minutes until it thickens.
Lower the heat and add the shredded cheddar and Gruyère cheese to the sauce. Stir until the cheese has fully melted and the sauce is smooth.
Mix in the cooked lobster meat, Dijon mustard, garlic powder, salt, and pepper to the cheese sauce. Combine well.
Add the cooked macaroni to the cheese sauce, stirring gently to ensure all the pasta is coated.
Pour the macaroni and cheese mixture into a greased baking dish. If you prefer a crispy topping, mix the breadcrumbs with the melted butter and sprinkle evenly over the mac and cheese.
Bake in the preheated oven for 20 minutes or until bubbly and golden on top.
Remove from the oven and let it sit for a few minutes before serving. Garnish with fresh parsley if desired.