Those juicy, crunchy, salty nubs called capers can bewilder those trying them for the first time. They look and taste a little bit as though they come from the sea, and I often think of them as the vegetarian equivalent of anchovies for their ability to add a bracingly salty punch to a dish. But they're as terrestrial as they come: Capers are the buds of a spiny Mediterranean shrub, and they're found most often in Mediterranean (especially Italian, Greek, and Provençal) dishes.
Capers are sold either packed in salt or, more commonly, pickled in brine. They range in size from under a quarter inch to over half an inch in diameter. You might also see larger capers, known as caperberries, which are what capers grow into if they're allowed to mature beyond the bud stage. Caperberries look quite a bit like green olives, only they're darker, have a stem, and contain crunchy, edible seeds rather than a pit.
The smallest capers are known as nonpareils (French for "without equal") and are considered the best -- which means, predictably, that they tend to be more expensive than bigger capers. I can't tell the difference, and don't think that pricey capers are worth the expense, even if you're planning to serve them straight up -- with good smoked salmon, for instance. When you cook with them, their strong flavor is balanced and somewhat softened by other ingredients anyway.
Cooking with Capers
I rarely use more than a couple of tablespoons of capers in a given dish for four to six people; their saltiness is so powerful that it can easily overwhelm a dish. It's a good idea to rinse capers -- especially the salt-packed ones-before you use them, and it's definitely a good idea to add salt sparingly to dishes containing capers. As usual, you can always add more later, but you can't take it away.
Slightly sweet ingredients help even out capers' aggressive saltiness and keep dishes containing capers from becoming one dimensional. Take puttanesca sauce, perhaps the most famous caper-containing dish. Puttanesca is essentially regular Italian-style tomato sauce with capers, anchovies, and olives added. Normally, using these three ingredients-among the saltiest in the home cook's repertoire-in a single dish would be overkill. But thanks to the natural sweetness of tomatoes and softened onions, the sauce is assertive but not offensive. Of course, you can adjust the ratio of ingredients to suit your taste -- if you like things pungent, use more capers or anchovies. If you prefer pasta on the milder side, use less -- or add half a teaspoon sugar along with the salt-containing ingredients.
A more unusual way to use capers, and one of my favorites, is to incorporate them into a rich, honeyed pan sauce for halibut. Normally using a quarter-cup of honey in a savory dish would result in a crazily cloying sauce, but against the acerbic capers and the delicate fish fillets the honey-butter tastes deep, rich, and not too sweet. If you can't find halibut, you can use any sturdy white fish. But you can't substitute for the capers; their flavor is truly without equal.