Meanwhile, heat a large, 12-inch, ovenproof Dutch oven or similar pot over medium high.
Add the milk, vegetable stock, garlic powder and macaroni; stir to combine.
Cover and bring to a simmer, stirring every minute or so to prevent the pasta sticking and to encourage even cooking; this takes about 4 to 5 minutes total.
When it comes to a simmer, stir well, reduce heat to medium-low, cover and cook until the pasta has softened and the liquid has thickened to resemble cream; about 5 minutes.
There should still be quite a lot of liquid coating the pasta; if it looks dry, add ½ cup of hot water; the pasta should be al dente, softened with a bite.
Add the cheese and stir until it melts and combines with the remaining liquid and becomes a cheesy sauce; season with salt and black pepper.