1. Preheat oven to 350°F. Coat a 9×13-inch baking dish with nonstick cooking spray. Bring a large pot of lightly salted water to boiling. Add pasta; cook al dente according to package directions. Drain; set aside.
2. Meanwhile, in a medium saucepan melt 1 tablespoon of the butter over medium heat. Add scallops; cook 3 minutes per side or until opaque. Transfer scallops to a plate; set aside.
3. In a large saucepan or Dutch oven melt remaining 3 tablespoons butter over medium-low heat. Stir in flour; cook and stir 2 minutes. Stirring constantly, gradually add milk; cook and stir 5 to 7 minutes or until sauce has thickened. Add Cheddar, Parmesan, salt and cayenne; cook and stir until cheese melts. Add pasta; stir to combine. Add scallops; gently stir to combine.
4. Transfer mixture to baking dish. Sprinkle evenly with panko. Bake 20 minutes or until bubbly. Remove dish from oven.
5. Preheat broiler to high. Broil 5 minutes or until golden brown. Let stand 5 minutes before serving.

Per serving: 592 calories, 21g fat, 11g saturated fat, 92mg cholesterol, 838mg sodium, 60g carbohydrate, 2g fiber, 41g protein

*5 minutes stand time extra