Separate the heads from the stems of the St George mushrooms.
Bring a pot with enough water to submerge all mushrooms to a boil.
Once the water boils, turn off the heat and let the mushrooms blench for 5 minutes.
Add a layer of salt to the bottom of your fermenting pot.
Add a layer of mushroom heads with the gills facing downwards.
Optionally add some wild garlic or other aromatics.
Add another layer of salt.
Add a another layer of mushrooms heads with the gills facing upwards.
Repeat the layering each time alternating the direction the gills face until the all mushrooms are in the pot. Remember to leave some space for the next step.
Add a freezer bag filled with water on top of the mushrooms to press the mushrooms down.
After a day check if the mushrooms are fully submerged in liquid, if they don't dissolve a teaspoon of salt in half a cup of water and add some of the water to the fermenting jar so the mushrooms are fully submerged.
Taste your mushrooms after 3 days, if the the taste is to your liking transfer the mushrooms to a container to store in the fridge to stop the fermenting process. If you want to mushrooms to be more fermented you can let them ferment for longer.
Notes
You can save the left over liquid from the fermentation process and use it as a vegan fish sauce.