Mac & cheese is an interesting dish because it speaks to us about comfort. however, what is comfort to one person is not to another. For instance, my late stepfather, who I admired and respected about most everything, loved mac & cheese that was made from government surplus American cheese. It was a creamy casserole style mac & cheese that was common during the depression years, and throughout the 1940's & 50's. To him, it was comfort food. I grew up with Kraft Mac & Cheese. To me, it's comfort food. Is it my favorite, not by a long shot.
The point I'm getting at is that mac & cheese is a personal kind of thing. A lot depends on what you like in cheese, the taste and textures you prefer. What I will tell you is that technique is important.
First, mac & cheese should be smooth and not stringy. This is accomplished by keeping the temperatures relatively low. You shouldn't let the cheese sauce boil as that can cause it to break, that is, the natural cheese oils and liquids will seperate out of the cheese and the protiens will clump together.
Second, it's easier to melt cheese into a sauce if you shred it fine and stir it in slowly. This is true whether you are adding the cheese to a roux-based white sauce, or to simple cream.
Third, remember that the pasta has a way of diluting the cheese flavor, and so sharper cheeses are generally used. But you can control that sharp flavor by adding other, milder cheeses to the mix.
Lastly, if the mac & cheese is baked in a casserole, it is best to use a round caserole dish to provide even heat distribution. This will avoid overcooked corners as are usually found in rectangular caserole dishes due to the concentration of heat in the corners of the cooking vessel.
Here are some cheeses and cheese combinations that will give you great results.
Sharp Cheddar - the most popular of cheese types used to make mac & cheese. The flavor is strong, very, if I might say, cheesey. It will require less cheese to add flavor to the pasta, but can be too strong if too much is used. Cheddar breaks easily in sauces and so must be grated fine, and mixed completely into the caserole. Pre-cook the pasta, add milk and butter to half fill the caserole dish with the pasta in it, and add the greated cheese, folding it into the still hot pasta. Cover with foil and bake in a 325 F. oven for 20 minutes. Remove the foil and sprinkle the top with more cheese, and if you like the top with a bit of crunch, some bread crumbs. Increase the heat to 375 and bake until the crumbs brown lightly (between seven to ten minutes.
Colby - colby is a form of cheddar, uniquely American. It is usually sold as a mild to medium aged cheese as it has a robust nature, similar to cheddar, but with a richer, more complex nature. Like cheddar, it breaks very easily in sauces. It is best blended with other cheeses, or crumbled, and sprinkled across the top of the casserole while other cheeses are mixed into the dish.
Monteray Jack - a semi-soft white cheese, with a texture between a young mozarella and American cheese. The flavor as a medium sharpness. This cheese melts well, but can be somewhat stringy. It is best used as part of a cheese mix. It works well with Muenster, and creamy cheeses like a butterkase, or havarti. This mixture should also contain either freshly grated Parmesano Regiano, Asiago, or Pecorino Romano to add a bit of saltiness.
Very young Mozzarella - this is a dreamy cheese with a mild flavor. It is soft and stringy when melted and has a wonderful mout-feel. It must be used with other cheeses though as its flavor is quickly overwhelmed by the pasta. Use with Fontina, Gouda, Havarti, or similar cheeses to add a salt componant and boost the cheese flavor.
American - A mildly acidic cheese with a pleasant flavor. I melts exceptionally well and is used by itself by many. Try using this cheese with something different, like a Port Salute, or maybe a good brick cheese.
Gorgonzola - a veined cheese with a rich flavor. This is great all by itself, or mixed with feta cheese, ricotta, or even cottage cheese. Just know that cottage cheese contains a fair amount of liquid and so can make your pasta caserole somewhat soupy if your not careful. One way to combat this is to use partially cooked pasta so that the noodles can absorb much of the liquid.
Of course there are a thousand different variations on this theme. Find the cheese that best suit your taste. Try making cheese sauces with them before trying them in mac & cheese.
The two best ways to make cheese sauce, IMHO, are:
Make a blonde sauce from a roux made from equal parts butter and flour, thined with milk to form a creamy sauce. Add the shredded cheeses slowly, stiring in each addition until completely incorporated into the sauce, over low heat.
Heat heavy cream in a pot until it just barely starts to bubble. REduce the heat and again slowly add the cheese/s, stirring untill all is smooth.
I can't tell you what the best cheese to use are, because it will be different for you than it is for me. So go on, experiment a little. See what you like.
Seeeeeeya; Goodweed of the North