How to tell Horse mushroom from White knight

The cap is 6-20 cm across; in young mushrooms it's firmly hemispherical to egg-shaped, often with the margin rolled under, later becoming convex to flat. The colour is pure white to cream, with subtle yellowish tints in old mushrooms; it stains yellow to ochre when touched. The surface is smooth, slightly sticky in wet weather, dry and matte in dry weather, sometimes with fine fibrous scales in the centre.

The cap is 4–10 cm across. Young caps are conical to convex with an inrolled margin, then flatten out around a small, low boss, often with a wavy edge. In the white knight the margin is smooth; a ribbed margin points more to the chemical knight of birch woods.

The colour is white to cream, sometimes with a pale yellow tinge. With age the centre turns ochre or yellowish brown, and old caps develop ochre spots. The surface is dry, matt and smooth, and stays dry even in rain.

The gills are free and crowded, greyish-white with a pinkish tinge when young, becoming dark brown to chocolate-blackish with age. The spore print is dark brown.

The gills are white, later pale yellowish, thick, fairly distant and of unequal length. They are clearly notched just before the stem, and their edges are finely toothed.

The spore print is white. Pink or chocolate-brown gills mean a field mushroom relative; gills running down the stem point to a funnel.

The stem is 6-12 cm tall and 1.5-3 cm thick, stout, fleshy and cylindrical, slightly thickened at the base, and white to cream. Near the top is a large membranous double ring with a characteristic "toothed" lower edge (like a cogwheel), a key feature of the species.

The stem is 3–8 cm tall and 0.8–1.5 cm thick, cylindrical, sometimes slightly wider at the base. It's white to pale yellowish brown, powdery at the top, finely fibrous lower down, and slowly browns when handled.

There is no ring, no veil remnants and no bag-like volva at the base. If you find such a sac, you're holding an amanita.

The flesh is firm, meaty and white; when cut, it slowly yellows in the cap and upper stem. It does not redden (unlike A. silvaticus). The smell is distinctly anise-almond, a characteristic feature of the species.

The flesh is white and firm, thick in the cap, and doesn't change colour noticeably when cut (some authors note a faint pink tint). The taste is acrid and burning, with bitterness.

Distinctly anise-almond and fruity, and this is the most telling feature. Rub the flesh between your fingers to bring it out. It's one of the most pleasant smells you'll come across while foraging.

The smell is strong and unpleasant: sharp like radish, with a sickly sweet note of honey and a mealy edge when cut. Young specimens smell less, mature ones can be smelt from a distance. A nauseating chemical smell, like cooked beetroot or coal gas, belongs more to its relatives, the chemical knight of birch woods and the gassy knight (Tricholoma inamoenum).