Prepare the veggies. Preheat the oven to 350. Cut the broccoli into florets (about 3 1/2 cups). Slice the carrots into thin coins.
Cook the pasta. Bring a large pot of salted water to a boil over high heat. Add the pasta and cook for 4 minutes, stirring occasionally. Stir in the broccoli, carrots, and peas. Bring back to a boil and cook for 2 minutes. Drain and pour into a 2.5qt baking dish.
Make the sauce. Return the pot to medium-high heat. Melt the butter, then whisk in the flour. While whisking constantly, let bubble for about 1 minute. As you continue whisking, add the milk 1/2 cup at a time. Whisk until smooth each time before adding more milk. Stir in the garlic powder, salt, and pepper. Reduce the heat to low and stir in the cheese. Cook for 1 to 2 minutes, until the cheese melts.
Bake. Pour the sauce over the pasta and veggies, stir, then top with the bread crumbs. Cover with aluminum foil and bake for 15 minutes. Remove the foil and bake for 5 minutes more. If the crumbs haven't browned, place the casserole under the broiler on high for 30-45 seconds. Enjoy!
