Bring water to a boil and add a pinch of salt before adding the macaroni. Let them cook for 18 minutes to keep the sauce creamier, stirring occasionally.
In the meantime, in a separate pan, pour the milk and add the mustard powder, milk powder, salt, and cornstarch. Mix and cook with occasional stirring until the cheesy sauce is warm. Put it aside.
Drain the cooked macaroni, and in the same pot add the warm creamy sauce. Mix well.
Add the cheddar cheese and Velveeta cheese and mix gently until everything is nice, smooth, and creamy.
Serve hot.
