There are a few species of Lactarius genus, commonly known as milk-caps, that are very popular salt pickled in Slavic cuisines, for example L. deliciosus/Ryzhik and L. resimus/Gruzd’.
Today in the U.S., mentioned above milk-caps are either unknown or deemed inedible, while in Eastern Europe they are traditionally considered among the best edible mushrooms. After removing the bitterness, they are salted and later enjoyed as a condiment (there is no better companion for a shot of ice-cold vodka!) or as an ingredient in other dishes. Salted mushrooms are fleshy, juicy, and have a unique flavor. In old times, salted gruzd’ was called “the king of mushrooms.” Wiki says, only in Kargopol county, annually there were up to 150 thousand pounds of milk-caps collected, pickled, and exported to St. Petersburg.
When gruzd or ryzhik mushrooms are not available, my second favorite are P. ostreatus/Veshenki or Oyster mushrooms. Luckily, they are farmed by Kitchen Pride just about two hours away from Austin, in Gonzales, TX.