Porcini or Bitter bolete

Cap 7–30 cm across, spherical or hemispherical in young mushrooms, becoming cushion-shaped and spread out over time. The color varies from light brown to dark chestnut or reddish brown depending on light and forest type: caps are darker in spruce woods and lighter in pine forests.

The cap surface is dry, smooth or slightly wrinkled, and can be a little sticky in wet weather. The margin is even or slightly wavy, inrolled in young mushrooms. The skin doesn't peel.

The cap of the bitter bolete reaches 4 to 15 centimeters across, and in especially good years you'll find real giants up to 20 centimeters. When young it is neatly hemispherical, opening with maturity to convex and later almost flat and spread out. The cap surface is dry, delicately velvety or finely felty to the touch in young mushrooms, but becomes smooth with age. The color palette ranges from light hazel and coffee brown to a warm ochre-brown, which especially heightens the deceptive resemblance to porcini.

The hymenophore is tubular and separates easily from the cap flesh. In young mushrooms the tubes are white, later turning yellow; in mature ones they're yellow-green or olive. The pores are small, round, uniform in color and don't change color when pressed.

Under the cap lies a tubular hymenophore, which is the main giveaway of this impostor. In very young mushrooms the tubes and pores are whitish, which, once again, recalls porcini, but very quickly they take on a characteristic dirty pink or flesh-pink hue. It's this pinkness that firmly sets the bitter bolete apart from true porcini, whose hymenophore can be white, yellow or olive, but never pink. When pressed or damaged, the pores often turn brown, developing rusty brown spots.

Stem massive, 5–20 cm tall and 3–10 cm thick, bulbous or club-shaped in young mushrooms, later cylindrical. Color from whitish to light brown. The surface is covered with a characteristic white or cream net pattern, most distinct in the upper part of the stem.

There's no ring and no volva. The base of the stem is often thickened.

The stem of the bitter bolete is massive and sturdy, 4 to 10 centimeters tall and up to 3 centimeters thick. It is swollen and club-shaped, especially thickened at the base, which makes the mushroom look stocky and dependable. The stem is colored in ochre-brown tones, lighter at the top and darker toward the base. The most important diagnostic detail is the net pattern: unlike porcini's delicate pale netting, the bitter bolete's net is distinct, coarse and dark, chocolate-colored or even blackish, and clearly visible to the naked eye. There is no ring and no volva at all.

The flesh is dense, juicy and white, and doesn't change color when cut or damaged — this feature sets porcini apart from a number of poisonous lookalikes. In old fruiting bodies the flesh becomes spongy and yellowish.

The taste is mild, nutty and slightly sweet. The stem flesh is denser and more fibrous than the cap flesh.

The flesh of the bitter bolete is thick, dense and fleshy, white or slightly cream-colored. When cut it mostly stays unchanged, although in some specimens it may turn faintly pink on exposure to air. There's none of the bluing typical of many boletes. But the flesh's main feature lies not in its color but in its taste: it is extraordinarily, unbearably bitter, like bile or quinine. It's this bitterness, which cooking doesn't destroy, that makes the mushroom unfit for the table.

The smell is pleasant, unobtrusive, mushroomy with light nutty notes. With cooking and drying the aroma intensifies and takes on a deep, rich woody, foresty character. It's for dried porcini that the mushroom is so valued in cooking — no other dried mushroom gives such a pronounced taste and smell.

The smell of the bitter bolete is faint and fairly nondescript, typically mushroomy, with no sharp or unpleasant notes. Unlike the taste, the aroma carries no warning at all and may well seem pleasant. That's exactly why you shouldn't rely on your nose to identify this species — the deceptively mild smell only adds to its overall resemblance to the noble porcini.