It’s a raw, chilly day, and San Francisco is wrapped in fog. As we put the final touches on this story, our very last, just-to-make-sure recipe test is in the oven. Mary’s apartment is filled with the cozy aroma of macaroni and cheese, and on a day like today, we can’t think of anything we’d rather eat.

Macaroni and cheese is the ultimate comfort food. Like many comforts, it’s best when you keep it simple and straightforward. The classic baked version is our favorite, based on a white sauce to bind the casserole, with Cheddar cheese stirred in. We also like a stovetop version, in which we experiment with stronger-flavored cheeses, melting them with some cream over very low heat before tossing in the pasta.

Use a gentle heat for a smooth cheese sauce

Whether you’re making baked or stovetop macaroni and cheese, you’ll need to cook the cheese over very low heat and for the shortest possible time. When cheese is overheated, the protein solids and the fat separate, and it gets stringy and rubbery

Baked macaroni and cheese needs a béchamel sauce to bind it.A béchamel is a simple white sauce that’s made by cooking equal parts melted butter and flour into a smooth paste (called a roux) and whisking in milk. Shredded cheese is added to the béchamel (which is now called a Mornay sauce). The starch in the roux stabilizes the cheese, keeping the sauce from separating as the macaroni and cheese bakes

Here are the keys to making a velvety, savory cheese sauce:

• Add flavor to the béchamel.We like to add a bay leaf, sliced onions, and whole peppercorns when we’re putting together the roux. You’ll strain them out before you stir the cheese into the thickened béchamel.

• Make a smooth sauce.Stir the roux constantly with a wooden spoon to avoid lumps, use a whisk when it’s time to add the milk, and keep stirring.

• Cook out all the flour taste.Cook the béchamel for at least ten minutes, or even twenty—you want to be sure there’s no starchy, pasty taste.

• Finely shred the cheese.The shreds will melt quickly when you stir them into the warm béchamel. Again, when you cook with almost any cheese, the heat should be gentle and the cooking time not too prolonged..

Experiment with a stove-top method

Stovetop macaroni and cheeseis a different approach—quick and convenient. You’ll get more intense cheese flavor this way, so it’s especially good for smaller, side-dish portions of pasta that you can serve with a plain main dish, and for more pungent cheeses, whose flavor can overwhelm in full-sized portions. We like to use blue-veined cheeses, such as gorgonzola and Roquefort, or to combine a few of our favorite Italian cheeses, such as full-flavored Taleggio and rich fontina.

For the stovetop mac and cheese, we combine the cheese and cream in a skillet and stir constantly over a very gentle flame, just until the cheese melts. Again, the heat needs to be as low as possible so the cheese doesn’t break and turn stringy, grainy, or oily. Toss the melted cheese and cream with the pasta and stir over low heat for a minute or two to let the pasta absorb the cheese sauce. We like to add a crunchy topping. If you just can’t wait, serve it right away, but it’s also good if you run it under the broiler for a couple of minutes to toast the topping.

Dry pasta is best for absorbing the cheese sauce

Use dry pasta made with semolina flour. It’s sturdier and more forgiving than fresh pasta, and it’s harder to overcook. And the shapes that are best for catching cheese sauce come in dry pasta form. Elbows are the classic, of course, but shells, bows, and rigatoni work well, too. We’ve always had success with De Cecco brand. Follow the package directions and cook the pasta in plenty of boiling salted water until it’s just barely tender. This prevents the pasta from getting mushy in the casserole.

Buttered bread crumbs add texture

A breadcrumb topping forms the crunchy top layer of this homey casserole. Use stale bread—the peasanttype makes especially good crumbs—and toss the crumbs with melted butter or olive oil. Simple, unflavored breadcrumbs work best on classic Cheddar macaroni and cheese, while crumbs flavored with garlic and herbs taste great on Parmesan macaroni and cheese. Mixing ground nuts with the breadcrumbs is a delicious complement to versions made with blue-veined cheeses.

Keep your variations simple

Lately we’ve seen versions of macaroni and cheese that throw in lots of new ingredients, but to us, that’s not macaroni and cheese anymore. One of the most pleasing qualities of this comfort dish is its simplicity

But one or two additions can make for inspired versions of this homey treat. Think about the cheese you’re using and what ingredient might complement it. Try these combinations:

• Parmesan with sautéed mushrooms
• Gruyère with peas and ham
• blue cheese with caramelized onion
• fontina with asparagus
• goat cheese with sun-dried tomatoes
• Cheddar with bacon.