Lactarius controversus is a large funnel-capped fungus within the genus Lactarius, which are collectively known as 'milk caps'. They all exude milky drops (lactate) from the flesh and gills when damaged.
It is distinguishable mainly by its pinkish-buff gills and rosy markings on the upper cap surface, often arranged in concentric rings. Like other fungi in the genus, it has crumbly, rather than fibrous, flesh, and when this is broken the fungus exudes a white milky liquid. Mature specimens are funnel-shaped, with decurrent gills and a concave cap. It has firm, tough flesh, and a stipe which is shorter than the fruitbody is wide. The spore print is creamy-pink in colour.
A similar species the Fleecy Milk-cap Lactarius vellereus, lacks the pinkish gills, and 'rosy' cap markings.
This mushroom is inedible due to its very acrid taste, and is probably best avoided.