Start by cooking the pasta as directed.Save 1.5 cups of pasta water. Drain the pasta and set aside.
In a pan or pot, melt the butter and add the flour. Mix until they are well incorporated.
Add the milk, pasta water, garlic powder, onion powder, salt and mix very well until you obtain a smooth creamy texture.
Add the cheddar cheese and mix again until the cheese melts and incorporates with the creamy sauce. At this point you can add the cooked pasta shells, broccoli florets and mix everything together one more time.
Let them cook for a few minutes until the broccoli florets are tender and then remove to serve.