TRUFFLES
Truffles are one of the most expensive foods available, and the price reflects the difficulty of finding them and of course the relatively high demand. Truffles make up the fruiting body of the Tuber genus and grow underground (which explains the problem of harvesting them!). In a sense then they are something like mushrooms although they have a very special flavor that goes well with meats, venison, or poultry. Their flavor and scent function mainly as an attractant for the animals that have the right sense of smell, and can find the truffle and eat it. In result, the animals' dung will leave behind and spread the spores of truffles - a way to reproduce the species, so common among the vegetables. The animals in the wild that eat truffles include squirrels and rabbits, but to find the truffles people use specially trained dogs or pigs. While the dogs must be trained in a special way to secure the sensory perception, pigs are naturally gifted for truffle finding. The problem is that the pigs love to eat truffles, so the hunter has to keep a good eye on the animal! For this reason, dogs are prefered in truffle hunting. They are trained in steps by learning them to find a normal ball, then a Gorgonzola cheese, and then a truffle - all foods that they normally don't eat and can be rewarded with meat for finding them. Another way to find the truffles is by looking for the swarms of the so-called truffle flies that hover above the truffled grounds.
Black truffles can cost about $500 for a pound, but their flavor is considered to be so good for complementing the food that chefs do buy them and serve them in their restaurants (for an extra price). To find a truffle, if you don't want to buy it, you need to further consider several success factors. First, make sure that there is no legal regulation concerning the soil you are walking on. In some regions, it is illegal to collect truffles unless you have a licence! Secondly, you need to wait for a warm weather and a moist soil. Truffles grow following a period of heavy rain, on the second week after the rain.
You also need to be in the right forest! Truffles grow in symbiosis (cooperation) with certain trees, like oaks, pines, firs, hickories, lindens, or hazels, and not with e.g. maples. The traditional truffle countries are France (black truffles) and Italy (white truffles), although they can be found in other places in the world, as long as the environment is right. The important thing to remember is that some truffles are not as flavorful as the famous French black winter truffles or the Italian Pico truffles. So, even if you find some other species around your place, they might not be so foudroyant in flavor. The same goes for truffles that are not ripened.
The flavor of black truffle is considered more interesting, as it is subtle, non-aggressive, and some has some "sweaty" flavors that some people don't like. White truffles on the other hand have a strong garlic-like aroma. In cooking, black truffles develop their flavor further, while the white truffles are better when served raw (their flavor is heat-sensitive).
Also make sure that the truffles you possibly find are really edible truffles and not some nascent form of poisonous mushrooms! Have it checked by someone who knows truffles!