In a large pot, bring salted water to a rolling boil. Add the elbow macaroni and cook according to package instructions until al dente. Once cooked, drain the pasta and set it aside in a colander.
In a large skillet, heat the olive oil over medium heat. Add the finely chopped onion and minced garlic, sautéing these together until they become soft and aromatic, about 2-3 minutes.
Incorporate the broccoli florets into the skillet, cooking for an additional 3-4 minutes until they begin to soften. Next, add the chopped spinach and halved cherry tomatoes; stir and cook until the spinach is wilted, approximately 2 minutes. Remove the skillet from the heat and set aside to cool slightly.
In a separate saucepan over medium heat, whisk together the milk and flour. Keep stirring continuously until the mixture begins to thicken, which should take about 3 minutes. Once thickened, reduce the heat and mix in the mustard powder, salt, and pepper. Gradually add in the shredded cheddar cheese, stirring until it melts entirely and the sauce is creamy and smooth.
Add the drained macaroni and the sautéed vegetable mixture to the cheese sauce. Gently stir everything together until it's thoroughly combined and heated through.
For a crispy finish, preheat your oven to 350°F (175°C). Transfer the mac and cheese mixture to a greased baking dish. Evenly sprinkle breadcrumbs over the top. Bake in the preheated oven for 15-20 minutes, or until the breadcrumbs are golden and the top is crispy.
Once baked, remove the dish from the oven and top with freshly chopped parsley for a burst of color and freshness. Serve hot, and enjoy your hearty, veggie-loaded mac and cheese!
Notes
Feel free to customize the vegetables based on your preference.