Panini sandwiches: crispy, gooey, and amazing. Right? Sure, but that description could be applied to any grilled cheese sandwich. What makes panini different from other grilled cheese?
The answer is grill marks. And not just the marks—although those are important, and they need to be a dark, golden brown. Panini need actual ridges. And to obtain those ridges, a panini needs to be pressed.
Using a Panini Press
One common method for making panini sandwiches is on an electric panini grill. It's a sandwich press with ridges. You place the sandwich on the bottom part of the grill, lower the top (which also has ridges and is also heated), and the sandwich is heated from both sides.
But here's a secret fact about panini presses (although if you've ever used one, it's not a secret to you at all): They never get hot enough!
Sure, they make the indentations, and they warm the sandwich up. But all too often, the grill marks they produce are disappointingly pale. The effect is closer to steaming than grilling, especially if the filling includes veggies. It's a little bit like what you'd get by leaving the sandwich on the dashboard of your car on a hot day.
Needless to say, a sandwich like this is wholly unworthy of the name panini, let alone your mouth. To make a proper panini, you need to generate a lot of heat.
Building the Sandwich
But first let's talk about building the sandwich itself. Ideally everything in a panini will be flat: flat bread, flat cheese slices, as well as all the other fillings. The flatter the fillings, the better the sandwich will heat through.
But note that other than the bread and the cheese, you're heating the sandwich, not cooking it. The cheese should melt, and the bread should turn brown and crispy. But any other ingredients should be cooked already (if you want them cooked). So if you're adding grilled vegetables, grill them first, separately. Same with any thin slices of meat, like chicken breast. That should be grilled and sliced ahead of time.
To build the sandwich, apply any spread, such as pesto or balsamic glaze, to the inside of both slices of bread. Then on one slice of bread, add the cheese, then the other ingredients, then finally, top with the second slice of bread.
Next, brush both sides of the outside of the sandwich with oil. Olive oil is great for this. And when you go to cook the sandwich, the side with the cheese should go down on the grill first, to ensure it gets as melty as possible.
Using a Cast Iron Grill Pan
And as we said a moment ago, we need lots of heat. That's where cast iron comes in. A cast iron skillet is the ideal pan for making grilled cheese. They get super hot and they apply their heat evenly. And since panini are sort of a cousin of grilled cheese, it makes sense to use the cast iron skillet's cousin, the grill pan, to make them.
A cast iron grill pan is simply a cast iron skillet that has the raised grill ridges built in. You heat it up, place the sandwich on it, and the ridges reproduce the marks you'd get by cooking on an actual grill. (Which is another way to make panini, and we'll get to that in a moment.)
Of course, it's not quite accurate to say that we simply "place" the sandwich on the grill pan. To produce the grill marks and the ridges, the sandwich needs to be pressed against the grill pan. That means something heavy needs to go on top of it.
You can purchase a cast iron grill press, which is just a slab or cast iron with a handle on it, and you plop it on top of your sandwich to press it firmly against the grill. It works a treat.
You can even get ridged ones. The idea is, you heat up the grill press along with the grill pan. Then when you cook the sandwich, the sandwich goes on the pan, the press goes on top, and it's heated from both sides, with grill marks.
Unfortunately, we run into the same problem here as we did with electric sandwich presses, namely, that the top doesn't get hot enough. You can heat the press all you want, but it won't be as hot as the grill pan below, which is sitting on the actual stove burner while it cooks.
The solution is simple. Grill one side of the sandwich using a grill press to hold it down, then when the cheese is starting to melt, turn it over and grill the other side.
Note, too, that you don't need to buy a dedicated grill press. Anything heavy will do: another skillet for instance. Or a tea kettle filled with water. Even a brick wrapped in foil.
Making Panini Directly on the Grill
It so happens that an outdoor grill is the best possible technique for making a panini sandwich. After all, what better way to get grill marks than on an actual grill?
Just heat your grill to medium, oil the outside of the sandwich, place it on the grill with a foil-wrapped brick over it, cook for two minutes or until the cheese has melted and you see dark-brown grill marks on the bread. Then turn the sandwich, replace the brick and grill for another two minutes, and voilà! Grilled, crispy deliciousness.