Copper brittlegillRussula decolorans

First make sure it really is a brittlegill: the flesh is brittle and snaps like chalk, there's no ring on the stem, no volva (sac) at the base, and the gills are white or cream. Only then touch a small crumb of the flesh to your tongue — and always spit it out, never swallow. If the taste is mild and bland, that's a good sign for a confidently identified brittlegill. If it's hot, burning, or bitterish, do NOT take it (these are toxic or conditionally poisonous species). Green and greenish brittlegills can be confused with the deadly death cap, so never taste a mushroom you haven't identified to genus. This isn't a universal rule — it only works within the genus Russula. The copper brittlegill tastes mild.

Yes. Gradual graying and darkening when cut is a characteristic trait of the species (hence the name "decolorans" — "losing color"). It's not a sign of toxicity. Gray spots on old mushrooms and in dead areas are normal too.

Pine and mixed forests with pine. Polissia (Chernihiv, Kyiv and Zhytomyr regions), the Carpathians, the Carpathian foothills, the Western Forest-Steppe. It loves acidic sandy and peaty soils and mossy patches. Less common in pure deciduous forests.

August — October, peaking in September. It loves a moderately damp, warm fall. In very dry or cold years it's rare.

The genus Russula has dozens of red and orange species. The copper brittlegill stands out by: 1) A gray-brown stem in mature mushrooms, 2) Flesh that turns gray when cut, 3) A mild taste (unlike many acrid red russulas). The gilded brittlegill (R. aurea) is yellower. The sickener (R. emetica) is burning-hot and doesn't turn gray.

Mainly with pine (Pinus sylvestris), less often with spruce (Picea abies) and birch (Betula). It's almost absent from pure deciduous forests.

Young, firm ones — pickle them or fry with onions. In old ones the flesh becomes brittle — good for stewing with vegetables. You don't have to peel the skin. Before cooking, boiling for 5–10 min is enough. You can dry it, but the aroma is weak.

In Finland and Scandinavia there's a well-developed tradition of picking brittlegills, and local mycologists tell the species apart well. Ukraine has the tradition too, but species in the genus get mixed up more often. The "taste test for acridity" helps weed out the burning-hot species, but only among mushrooms you've already identified for certain as brittlegills (brittle flesh, no ring, no volva). It doesn't protect you from the death cap.