Koreans pickle shiso with salt and Korean dried chilies (which are less spicy than most Japanese varieties, and therefore used in copious quanitities). It's a slightly different variety but very similar. My favorite thing is to take some parboiled (20 minutes or so instead of 30) rice and barley, mix with pine nuts and a bit of salt, and wrap the rice in small bundles of these pickles, like dolmas. I put them in a baking dish and add soup stock (vegetable, in my case, or whatever you like); bake until most of the soup is absorbed in the rice. My Korean teacher was all over this, even though the dish was clearly fusion.
Shiso is also a good accompaniment for a nontraditional
hiya-yakko: Cold oborodoufu or other good fresh soft tofu, a seeded chopped umeboshi, and a bit of fresh shiso chiffonade; add a modest drizzle of Japanese soy sauce.
I have used it in place of basil for a
harumaki caprese: good tomatoes and passable mozzarella wrapped inside a shiso leaf; wrap inside small harumaki-no-kawa or gyouza-no-kawa, a la spring rolls. Fry until golden.
To use a bunch of it fast, puree shiso with pine nuts, garlic and olive oil. If you can make pesto with basil or arugula, there's nothing wrong with a
shiso pesto. With a very mild cheese it works on pizza; you can use it in a wa-fu spaghetti dish, perhaps, or any dish where a little green mintiness would dress it up a bit.
A local bar in Seattle makes a cocktail called "
moshiso", which starts with shiso leaves bruised against a healthy spoonful of sugar; add a hefty shot of rum and sufficient lime juice (or yuzu juice, but they don't have it available to them). A smart interpretation of a mojito.
I think a few Japanese and Korean companies have been making a shiso "juice" syrup using red shiso. I am not sure of the exact formulation, but I would bet it is a healthy amount of shiso leaves boiled with a 1:1 simple syrup, strained or filtered, and perhaps blended with citric acid. It works nicely as a base for drinks and salad dressings.
If you have a way of using basil, mint, or other similar herbs, you might use it as a jumping off point.
Shiso is my favorite Japanese herb. I started growing it in pots in my yard, and now I have a few plants with huge beautiful purple leaves.

