01 - Preheat oven to 350°F (180°C). Coat a medium-sized baking dish with nonstick spray or butter.
02 - Steam or blanch broccoli florets and carrot slices for 3 to 4 minutes until just tender. Drain thoroughly and set aside.
03 - In a medium saucepan over medium heat, melt the butter. Whisk in flour and cook for 1 minute, stirring constantly. Gradually whisk in milk until smooth. Cook until thickened, about 2 to 3 minutes.
04 - Remove saucepan from heat. Fold in shredded cheddar, garlic powder, onion powder, salt, and pepper. Stir until cheese is completely melted and sauce is creamy.
05 - Gently fold the blanched broccoli and carrots into the cheese sauce, ensuring even distribution. Transfer the mixture to the prepared baking dish and spread in an even layer.
06 - In a mixing bowl, combine panko breadcrumbs, melted butter, and grated Parmesan if using. Sprinkle the topping evenly over the vegetable-cheese mixture.
07 - Bake for 25 to 30 minutes until the top is golden brown and bubbling. Remove from oven and let rest for 5 minutes before serving.