Chestnut bolete or Cornflower bolete

Cap 3–12 cm, hemispherical in young mushrooms, then flat-convex or flat. Color chestnut-brown, reddish-brown, sometimes lighter — hazel. The surface is dry, finely felty to the touch, and may crack slightly in old mushrooms. The skin does not peel off.

Cap 5–15 cm, hemispherical in young mushrooms, then cushion-shaped, almost flat in old ones. Color cream, pale yellow, ochre-yellow, darkening with age to brownish yellow. Surface matte, slightly felty or finely cracked in dry weather. The cap skin does not peel. Turns blue instantly when pressed.

Pore surface of tubes, white at first, then yellowish to straw-colored. Pores small and round. They do NOT turn blue when pressed — this is the key difference from its relative Gyroporus cyanescens.

Hymenophore tubular, white at first, then yellowish, straw-yellow in mature mushrooms. Pores small and round. When pressed they quickly turn blue, then black — one of the key diagnostic features of the species.

Stem 4–8 cm tall, 1–3 cm thick, cylindrical or slightly tapering toward the base. Same color as the cap or a little lighter. The surface is finely felty. The most distinctive feature: in mature mushrooms the stem is hollow inside, with uneven chambers — like dried bamboo.

Stem 3–12 cm tall, 1–3 cm thick, cylindrical or slightly swollen at the base. Same color as the cap or a little paler. Smooth at the top, sometimes with barely visible veins lower down. In young mushrooms the stem is solid; in mature ones it has hollow chambers inside (also a diagnostic feature of the genus Gyroporus). Quickly turns blue when cut or touched.

Flesh white, brittle, does NOT change color when cut (an important feature — other boletes with a chestnut cap often turn blue or pink). Hollow in the stem of mature mushrooms.

Flesh white or cream, brittle and fragile, chambered in the stem of mature mushrooms. Exposed to air, within 2–5 seconds it turns a vivid blue, cornflower color — the fastest reaction of any bolete. After a few minutes the blue fades to grayish blue.

The smell is faint, pleasantly mushroomy with a hint of nut. The taste is mild, sweetish, reminiscent of a real chestnut.

Smell faint, pleasantly mushroomy, with a note of fresh hazelnut. Taste mild, with no bitterness or spicy notes.