With the spread of Panera Bread, panini have become familiar foods for many Americans and, as princess loulou informs me, have been familiar to Europeans for years. Roasted vegetables, pesto and brie or mozerella, spicy chicken, and italian cured meats are all popular ingredients. They are delicious and easy to make, and are a nice way to make sandwiches a little more exciting than the usual fare.
The panino is really nothing but a big heated and pressed sandwich made with ciabatta bread, which most grocery stores have in the bakery section. Ciabatta is somewhat firm and has herbs and sometimes slices of onion on the outside. The crust covers the entire outside of the bread because it's not sliced. Panini are normally cooked using a panini press, which is a gadget that looks like a double-sided George Foreman Grill with a handle you can press down on.
My panino recipe
I always need a big plate for this, because everything tends to spread out. I plug in the panini press and set it to Medium so it can heat up. I cut the bread in half, so that there are two large, thin slices. I take a brush and put a bit of olive oil on the outside so that it will get crispy. I like that. I spread some pesto on each side of the bread, and then I sprinkle some feta on the bottom piece. I lay out some of the tomato slices on top of the cheese, then I put 3 or 4 mushroom slices on that, enough to cover it. I sometimes put more cheese on top if I feel like I didn't put enough on the bottom (and if it will stay), and after all of that I put the top piece on top of the bottom piece. At this point, the press should be heated, so I put the whole thing in there. Most of the time it doesn't fall apart. Sizzle... I love that sound. Anyway, I press down on it to make it manageable throughout the process. It will sizzle forever if you let it, but be mindful of it, and don't let it burn. I consider a panino done when it is golden brown all over, and nothing leaks out when I squish it.
Panini are pretty big, so they can be shared between two or more people. They don't take very long to make and I'm sure they're healthier than a hamburger. Of course, you can put anything in a panini that you want. It is, after all, a sandwich.
Panini is plural. Panino is singular. Blame Italy.