A grilled cheese sandwich is an ode to childhood, a purist's dream and an archetypal comfort food all at once. Just three mundane ingredients and a few minutes should be all it takes to create something downright sublime, right? So why do so few sublime ones come our way?

As with other minimalist dishes — an omelet, say, or a plate of pasta — there are a lot of assumptions that can get in the way of the cooking, assumptions that need to be jettisoned before the dish can reach its true potential.

When done right, an exemplary grilled cheese sandwich is not grilled (it's toasted). Nor is it quick. And it certainly doesn't shine when it's assembled from just any cheese or bread. But combine slow griddling over a low flame with a cave-aged Gruyere, a loaf of freshly baked country bread and a nub of Normandy butter, and you'll have a simply made dish that approaches greatness.

High-quality bread, butter and cheese are already a magical combination; when toasted, that magic becomes transformative. The ingredients undergo a rough alchemy, the butter browning, the bread crisping, the cheese melting into a glorious synthesis, shot through with a rich, caramelly perfume.

This magic is so strong that for many of us, it worked throughout childhood with squares of American cheese, pillowy white bread and margarine. Imagine the results with artisan cheeses, terrific bakery bread, creamy butter — maybe some stone-ground mustard or slices of heirloom tomatoes — and, importantly, a little grown-up patience.

Because along with great ingredients, the secret to a perfect grilled cheese sandwich is in the timing. Don't rush it. The bread needs slow encouragement to crisp evenly; the cheese is best when it's coaxed into melting.

In spite of its name, a grilled cheese sandwich should not be grilled. The bread will char long before the cheese melts. A cast-iron pan or griddle works best because it retains and diffuses the heat more effectively than other pans. You'll also need a weight or press.

Slow diffusion of heat and weighting the sandwich allow for even cooking and happy results — a wide expanse of golden bread and, above that, an even field of melted cheese. Cooking it evenly means that when you flip the sandwich, the process continues on the other side: no pockets of unmelted cheese, no periphery of untoasted bread, no soggy interior.

The easiest thing is to place a second, smaller cast-iron pan on top of the sandwich as it cooks. The weight condenses the cheese, pressing out air pockets, and flattens the edges of the bread so they remain pressed firmly against the heated surface.

BREAD? USE THE BEST

The best bread for making grilled cheese sandwiches is freshly made and sliced (ask the bakery to do it when you choose the loaf so that you have uniform half-inch slices) — maybe a country white sourdough or a light whole-wheat. Dense whole-grain loaves tend to be too heavy; baguettes and some ciabattas can be shot through with air pockets — gorgeous when sliced, maybe, but not the best vehicle for melting cheese. And though you might think that stale bread would make pretty good grilled cheese sandwiches, the already brittle crumbs can become like shards when crisped.

Choose a cheese that melts well, neither as hard and pungent as Parmesan nor as soft and creamy as a Camembert or a fresh goat cheese. Even when grated, harder cheeses won't melt satisfactorily, and soft cheeses won't hold up to the cooking but will leak out of a sandwich and into the pan.

Widely available cheeses such as Gruyere, Fontina and Emmentaler are fantastic for this purpose, as are the whole gamut of cheddars, made in Wisconsin or Vermont or England, aged for six months or three years, or maybe smoked over apple wood. Blue cheeses, if not too gooey or overwhelmingly pungent, can make for pretty tasty sandwiches too. Be sure to slice the cheese very thinly, or better yet, grate it. It's a bit messier, but it melts the most evenly.

You can also play with flavor profiles (and textures) and mix two or even three cheeses. Just be careful to match cheeses that have complementary flavors and melting points, and be careful not to overdo it.

With a terrific cheese, it's easy to think that more is better, but restraint is actually crucial to a good sandwich. There should be a good proportion of bread to cheese, about twice as much bread as cheese. Though this ratio can vary according to taste, too much cheese can be overwhelming. (If this becomes a recurrent problem, consider making fondue instead.)

To bring it all together, choose a good butter; if you're feeling particularly decadent, try salted Normandy butter. It adds a certain extra luxuriousness to the sandwich, and the added hint of salt further brings out the flavors of the bread.

Melt the butter first, as it makes it easier to move the sandwich from the cutting board to the pan, and to weight it without the butter sticking to the various surfaces.

You could also brush the bread with a fruity olive oil for a more robust, earthy flavor, which is a nice option with an aged goat cheese or a nutty Emmentaler. And, if you use a mild cheese such as Fontina or Muenster, try infusing the olive oil with fresh sage leaves, peppercorns or rosemary. Or use a combination of olive oil and butter.

Though a purist will stop here, you can also embellish a grilled cheese sandwich with further accouterments. Torque up the classic Gruyere and country white sandwich with a smear of whole-grain mustard and some marinated onions like chef Mark Peel does at Campanile restaurant in Los Angeles. Add smoked ham or apple-wood-smoked bacon to a robust blend of sharp cheddar, Muenster and Fontina.

BE DIFFERENT

Experiment with flavor combinations: Spread rosemary bread with tangy apple butter for a spin on the traditional pairing of apples and cheddar. Match fig preserves with an aged goat cheese and walnut bread, or put together a smear of chestnut honey with a rich Basque blue cheese and crisp raisin brioche. You can spread the preserves or honey on the bread before adding cheese and griddling it — or add a spoonful to the plate for casual dipping.

Sandwich in a few thin discs of pear with a mild blue cheese, thin slices of prosciutto with Fontina or heirloom tomatoes. But take a tip from "Nancy Silverton's Sandwich Book" (born of Grilled Cheese Nights) and add the tomatoes after the sandwich is cooked.

Let a few slices of tomato sit under a brief pour of olive oil and a sprinkle of sea salt while you cook your sandwiches. When the sandwiches emerge from the pan, burnished and redolent of melted cheese, pry them open and gently slide in the tomatoes.

It's the perfect solution, too, for other delicate add-ins that can't stand up to the heat of the pan — such as fresh herbs, tender baby lettuces or ripe peach.