Preheat oven to 350 degrees. Place macaroni and kosher salt into a large saucepan of boiling water. Boil 7 minutes and drain. In a medium saucepan over medium heat, melt 6 tablespoons butter. Stir in flour to make a paste. Slowly add milk and stir until milk is hot. Add Gruyere cheese, stirring until melted. Add cheddar and Swiss cheeses, stirring until melted. Stir in salt and pepper then remove from heat. Stir in crab meat and drained noodles. Spoon into a greased 3 quart casserole dish. Sprinkle with Parmesan cheese and breadcrumbs. Drizzle remaining butter over breadcrumbs. Sprinkle with fresh parsley. Bake, covered, for 45 minutes. Remove cover and bake an additional 15 minutes. Remove from oven and allow to sit for 5 minutes before serving.