Oven-Baked Lobster Mac

Ingredients

• 1 (16-ounce) box cavatappi or cellentani pasta
• 1/2 cup unsalted butter, divided
• 1 small onion, diced
• 2 cloves garlic, minced
• 1/2 cup all-purpose flour
• 1/2 cup chicken or vegetable broth
• 3 1/2 cups milk, warmed to 115 degrees F
• 4 cups Gruyère cheese, shredded
• 2 cups cheddar cheese, shredded
• 1 cup parmesan cheese, grated, divided
• 2 teaspoons kosher salt
• 1/2 teaspoon black pepper
• 1/2 teaspoon nutmeg
• 1 1/2 pounds lobster meat, cooked
• 1/4 cup panko breadcrumbs
• fresh parsley, to taste, chopped, for garnish