01 - Preheat oven to 350°F. Lightly grease a medium baking dish and set aside.
02 - Steam or blanch broccoli florets and carrot slices for 3–4 minutes until just tender. Drain thoroughly and reserve.
03 - In a medium saucepan over medium heat, melt butter. Add flour, whisking constantly, and cook for 1 minute until smooth.
04 - Slowly pour in milk while whisking until a smooth, thick sauce forms. Remove from heat. Stir in cheddar cheese, garlic powder, onion powder, salt, and black pepper. Mix well until cheese is fully melted and the sauce is creamy.
05 - Fold steamed broccoli and carrots into the cheese sauce, ensuring vegetables are evenly coated.
06 - Transfer cheese-coated vegetables to the prepared baking dish, leveling the surface.
07 - In a mixing bowl, combine panko breadcrumbs, melted butter, and Parmesan cheese if using. Sprinkle the mixture evenly over the vegetables.
08 - Bake in preheated oven for 25–30 minutes until the top is golden and the cheese sauce is bubbling. Remove from oven and let stand for 5 minutes before serving.