In a large pot of salted boiling water, cook the elbow macaroni according to package directions until al dente. Drain and set aside.
In a large skillet, heat olive oil over medium heat. Add the chopped onion and minced garlic; sauté until softened and fragrant, about 2-3 minutes.
Stir in the broccoli florets and cook for another 3-4 minutes. Then add the chopped spinach and halved cherry tomatoes, and cook until the spinach is wilted, about 2 minutes. Remove the skillet from heat and set aside.
In a saucepan, whisk together the milk and flour over medium heat. Stir continuously until the mixture thickens slightly, about 3 minutes. Lower the heat and mix in the mustard powder, salt, and pepper. Gradually add the shredded cheddar cheese, stirring until melted and smooth.
Add the drained macaroni and sautéed vegetables to the cheese sauce. Stir everything together until well combined and heated through.
If you’d like a crispy topping, preheat the oven to 350°F (175°C). Transfer the mac and cheese mixture to a baking dish. Sprinkle breadcrumbs on top and bake for about 15-20 minutes, or until the top is golden and crispy.
Once cooked, remove from the oven and garnish with freshly chopped parsley. Serve hot.
Notes
Add more vegetables as desired; use gluten-free pasta for a gluten-free option.