Royal bolete or Oak bolete

Cap 5–15 cm, hemispherical in young mushrooms, then cushion-shaped and flattened-convex. Color pinkish raspberry, pinkish red, darkening with age to brownish red. Surface matte, slightly fibrous in dry weather, a little slimy in wet weather. The cap skin does not peel. The cap margin is rolled inward at first, then straightens out.

Cap 6–20 cm, hemispherical in young mushrooms, then flat-convex to cushion-shaped. The color varies: brown, yellow-brown, olive-brown, darker in the center. The surface is dry, slightly sticky in wet weather; in mature mushrooms it may crack finely into soft patches.

Hymenophore tubular, free or slightly notched at the stem. Lemon yellow, turning ochre-yellow with age, olive in old mushrooms. Pores small and round. When pressed it may turn faintly blue or not change color at all — unusual for a bolete.

The spore-bearing surface is made of tubes, with a slight notch near the stem. The color is rich yellow (a buttery yellow — hence the genus name "butyri"). The pores are small and round. When pressed they may turn slightly blue, especially in mature mushrooms.

Stem 5–14 cm tall, 2–6 cm thick, bulbous at the base, then cylindrical. Color lemon yellow to ochre-yellow, with a clearly visible fine net on the upper part (a hallmark of the genus Butyriboletus). Sometimes with a pinkish tinge at the base.

Stem 5–15 cm tall, 2–6 cm thick. Thicker near the top; toward the base it sometimes tapers or has a cone-shaped "appendage" (hence appendiculatus). Yellow in color, with a barely visible fine net in the upper part, sometimes with reddish-brown spots at the base.

Flesh lemon yellow, reddish under the cap skin, very firm and heavy. When cut, the color does not change or turns slightly blue in spots. This is another important diagnostic feature — most pink-capped boletes turn blue instantly and strongly.

The flesh is buttery yellow, very firm in young mushrooms, softer in mature ones. When cut it may slowly turn blue, especially in the tubes and the upper part of the stem. At the stem base it sometimes has a pink or reddish-brown tint.

Smell faint, pleasantly mushroomy, with notes of fresh hazelnut. Taste mild, sweetish, with no bitterness and no peppery notes.

The smell is pleasant, mushroomy-nutty, with a faint note of fresh forest berries. The taste is mild and earthy, with no bitterness — some sources describe it as "buttery nuttiness".