Stack the leaves putting a fine layer of sea salt in between every other leaf.
Put the leaves into a glass or ceramic bowl with just enough pure water to cover. Leave for several hours or overnight.
In a separate bowl, mix the rest of the ingredients together until you get a loose paste.
Using a butter knife or the back of a spoon, spread a little bit of the paste in between every other leaf, until all the chili paste is used up.
Fold up the whole stack and place into a clean, sterile Mason jar or fermenting crock.
Add pure water until the leaves are covered, then close the jar loosely, or use an airlock fermentation lid.
Leave in a cool, dark place to ferment. This takes about a week, though in cool weather it could take longer.
Unless you are using an air-lock fermenting lid, you should check the lid every day to see if any fermentation gas needs to escape.
Serve a small plate of the leaves to be eaten as a banchan (side dish), mince the leaves into vegetables or salads for a spicy kick, or eat your fermented shiso by wrapping a leaf up with some lettuce and bulgogi (Korean BBQ).