Deep Purple Hue When Young

 Shades of lilac and lavender make young L. nuda easy to differentiate, but the colors fade with age and exposure to the elements to tans and greys. 

Crowded Gills

 The tightly packed gills are light violet to buff and will drop a pinkish-to-white spore print. The gills will often be adnexed or sinuate. 

Stipes

 Usually growing individually, the stipes of nearby fruitbodies may  fuse. Stipes are often striate or finely fibrous in external texture.  They are equal in width or bulbous towards the base. 

More about Lepista nuda

Growth

L. nuda are saprobes (they eat decaying material) and will be found growing on the ground (not wood) individually or gregariously, sometimes attached at the base of their stipe. Look for areas of decaying leaves shaded by tall grasses in the cooler months.

Like many other saprobes, these can be cultivated, or at a minimum encouraged to grow in mushrooms beds.

Pick Young

These fruitbodies can be some of the last respites for bugs before it gets cold, so pick Lepista when young and prior to the cap unfurling completely, if you can.

Prep

Lepista species are probably most akin to a more moisture-dense portobello mushroom and can be cooked in similar ways. The stipe may be more tough and require more cooking time.

Cortinarius

Especially C. iodes, C. iodeoides and even the pictured C. violaceus. Similar in color and habitat, often occurring at the same time of year. These will drop a rust-colored spore print and many will have wider spaced gills. 

Several species of this genus are toxic.
Find out more here.

Laccaria

Cap and gill colors can be  similar and they appear at about the same time of year.

Lapista sordida



L. sordida is not easily seperated from L. nuda. It tends to be slightly smaller and less robust than L. nuda. It also has a thinner cap margin when mature. It is also considered edible. 

Lapista tarda



L. tarda tends to be more pinkish-brown than L. nuda. Its flesh is also more thin and brittle. Margin tends to be wavy reported in various texts as edible and inedible, it is reportedly bitter tasting.