Lobster and Cheese Pasta

Gather all the necessary ingredients before commencing with the recipe.\nBring a large pot of salted water to a rolling boil and cook elbow macaroni until it's tender yet still retains some firmness in the middle, approximately 8 minutes. Set aside 2 cups of hot pasta water and then drain the macaroni in a colander placed in the sink. Rinse it with cold water to cool down and then put it aside.\nPour the reserved pasta water into the same pot, add lobster halves cut-side up, and bring to a boil. Once boiling, reduce the heat to medium-low, cover the pot, and let it steam for about 3 minutes until the lobster meat becomes firm and opaque.\nTransfer the lobster to a tray, let it cool for a few minutes, then remove the meat and cut it into bite-sized pieces. Set aside the lobster shells.\nMelt 2 tablespoons of butter in a saucepan over medium heat and cook the onion until it's softened and translucent, taking about 5 minutes. Transfer the onions to a small bowl and set it aside.\nCombine the reserved lobster shells, milk, shallot, peppercorns, and garlic in the same saucepan. Bring it to a gentle simmer over medium heat and let it cook for 20 minutes.\nPreheat the oven to 350 degrees Fahrenheit (175 degrees Celsius).\nMelt the remaining 5 tablespoons of butter in a separate saucepan over medium-low heat. Whisk in flour and cook until the mixture turns light golden brown and pasty, taking about 10 minutes. Strain the milk mixture through a mesh sieve and slowly pour it into the flour mixture while whisking. Bring it to a simmer over medium heat, cook and stir until thick and smooth, taking about 10-15 minutes. Remove from heat.\nStir the Gruyère, Cheddar, and Romano cheeses into the thickened milk mixture until melted and smooth. Season with salt and pepper, then stir in the reserved lobster meat, onions, and macaroni.\nPour the mixture into a 4-quart casserole dish, smooth the top, and sprinkle it evenly with panko crumbs.\nBake in the preheated oven until the sauce is bubbly and the top is golden brown, taking about 8-12 minutes.