The grilled cheese sandwich. Three ingredients. So many possibilities.

First, the bread

Metropolitan San Francisco Sourdough, Le Bus Stirato, Philly Bread Pullman, Marble Rye, Night Kitchen Dakota, challah, Le Bus Raisin Walnut.

Then, the cheese

Something creamy for texture — red-wax Gouda, Havarti, Cooper Sharp, mild Cheddar, smoked Gouda, Monterey Jack, Colby, Gruyere. I think mixing is the best way to go. A cheese plane and box grater are valuable tools here. Grate some aged or extra-sharp cheese like Asiago, sharp Provolone, 3-year-old Canadian Cheddar, Manchego or Parmigiano-Reggiano. You want a ratio of about 60 percent creamy-melty cheese and 40 percent aged sharp cheese.

(Not an exact science, of course.)

Finally, the fat

Butter, oil or mayonnaise? My experiments have proven that all bring successful and delicious results, with subtle differences. The method that works best is spreading the butter or mayonnaise on the bread and coating the pan with a bit of oil (canola or olive), just with a paper towel. Keep the heat low and have a cover handy. Some people grill both pieces of bread and then put them together, but I keep the sandwich together and flip it. By the time one side is golden brown, the cheese will be melted enough to keep the other slice of bread in place. The difference between using butter as opposed to mayonnaise is that the mayonnaise-coated bread has a crispier texture and a bit of a tang, while the buttered bread is more caramelized and rich.

Part of my education on this subject came from an expert — a 7-year-old boy named Benjamin, the son of my best friend Lizzie. He is a purist: No spreads and no tomato. But a dipping “sauce” can be delightful. The beauty of sauce on the side is that you keep the integrity of textures and flavors of a well-made grilled cheese sandwich. Benjamin’s sauce of choice was ketchup. Hey, don’t knock it until you try it.

We could talk at length about other pairings but this story is focused on the bread, cheese and fat.