How to tell St George's mushroom from White knight

The cap is 5-15 cm across (large and fleshy). Young caps are hemispherical with an inrolled margin, becoming flat-convex with age, and in old mushrooms flat and spread out with a wavy margin. The skin is smooth, dry and matte in wet weather, with a fine felty fibrousness. The colour is creamy white or ochre-cream, with a faint brownish tint at the centre; old caps are creamy ochre. The margin is even: inrolled when young, wavy and irregular when old.

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 notched (emarginate) at the stem, very crowded, thin and fleshy. They're pure white to creamy white, with no pink or green tint, which is a diagnostic feature: it sets the mushroom apart from the poisonous Entoloma sinuatum, whose gills turn pink. The spore print is white.

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 3-7 cm tall and 1.5-3 cm thick, much shorter and thicker than the cap is wide (hence gambosa, "short-legged"). It's cylindrical, thickening toward the base, firm and fleshy, white to creamy white, and smooth, with fine lengthwise fibres in the lower part. There's no ring.

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 very firm, fleshy and pure white, and it does not change colour when cut. The smell is distinctly mealy, sharp and characteristic (like freshly milled flour or dough); the taste is sweetish and nutty, with no bitterness.

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 mealy, like freshly milled flour or raw dough — a diagnostic feature, easy to notice on a cut surface.

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).