Macaroni and cheese is almost never just macaroni and cheese. Typical recipes include milk or cream and a flour-and-butter roux to make a sauce base into which the cheese is melted -- plus any number of add-ins from prosciutto to mushrooms. And I shall merely mention the fact that one version of the stuff in a cardboard box contains 20, few of which count as food.
But with the right cheese you can quickly cut the ingredients list to the two items in the dish's name (plus salt, pepper and water for boiling the pasta). What is the right cheese? It is one that melts into a smooth, creamy sauce that won't seize up and turn to concrete. And it is one whose flavor has complexity and interest enough that it needs no help.
For me, that cheese is gorgonzola, specifically gorgonzola cremificato, which has those attributes in spades. It is at once creamy, blue-cheese-moldy and piquant, and it melts into as smooth a goo as, dare I say it, Velveeta. It is sometimes sold sliced from a somewhat amorphous blob, and sometimes, if it is especially soft, scraped into a container. Its rind is edible, though I tend to remove most of it for this dish for aesthetic reasons.
Besides there being nearly no shopping list, there's almost no recipe. For two portions: When a pot of salted water comes to the boil, add 200 grams (or half a pound, which is a little more) of short pasta and cook it until done. While that is happening, put five or six ounces of gorgonzola cremificato into a skillet and melt it over low heat, stirring and prodding it with a rubber spatula or wooden spoon. If you cannot find this particular cheese, normal "sweet" gorgonzola will work well, too, but you'll need to add a couple of tablespoons of milk to the skillet to help it melt into a sauce.
When the pasta is done, drain it (saving some of the cooking water) and stir it into the melted cheese. If necessary add a little of the water. It won't need salt, but you may want to grind in some black pepper -- I always do.
You can call it Cappelletti with Gorgonzola Cremificato if you like, but I say it's macaroni and cheese and nothing but macaroni and cheese.