They should be clean, unblemished and firm, with the cap securely attached to the stem. They are best young.

Keep in a cool, dark place. Refrigerate.

Can be kept in oil.

They retain all their flavour when dried. Place them on a platter at room temperature or in a very low oven. Once dried, they can be pulverized to be used in many dishes, or else rehydrated in cooking liquid.

Young boletus mushrooms can be eaten raw.

It is best to remove the tubes on the underside of the mushroom which have a tendency to become slimy.

Never soak mushrooms in water - they are like sponges and will soak up the liquid. 

Scrape them with a knife blade or brush them off. The caps can also be wiped clean using a damp cloth. Cut off any spoiled sections as well as the earthy bottom of the stem.

Mushrooms can be cooked in a pan with or without fat, but always on low heat to start, in order to "sweat" them.

When their cooking water has evaporated, they can then be braised or sautéed.

Corsica
There are many varieties of boletus which are grilled and then napped with a tomato and mint sauce - a specialty of Castagniccia

Hungary
Sautéed in butter with minced onion, salt, pepper and paprika. Finish with cream.

Auch
Cooked in white wine

Perigord
In sauces, combined with meat juices, in fricassees or omelettes

Italy
In carpaccio - very thin slices of beef or game, sliced boletus mushrooms, olive oil, French shallots, garlic, balsamic vinegar

Switzerland
With cream and veal escalopes dipped in egg, flour and fried in butter