I have used the flowers and seedpods as a garnish/decoration and seen commercial Tsukudani of shiso seedpods 紫蘇の実の佃煮 but never thought of making it myself until I came across the post from one of the blog I follow (in Japanese). I think the major effort required to make this dish is to remove the seedpods from the stalks.
The image above on the left and center are seedpods attached to the stalk and the right is after separating pods from the stalk. This is a rather time consuming tedious step (My wife helped me). I washed the pods with stalks and let it dry before removing the seedpods. I would have only used mirin, sake and soy sauce for the seasoning like I did with kelp tsukudani, but I followed the recipe from the aforementioned blog and also added rice vinegar (at the very end of the cooking) and umeboshi.
It tastes somewhat like any tsukudani (salty soy sauce and molasses-like sweetness) but has a nice popping crunchy texture when you bite down on it (Japanese expression is “puchi puchi” プチプチ). It doesn’t have much perilla taste per se but it does have interesting flavors. Certainly, this will be very good to just nibble while drinking cold sake or on hot rice. We actually tried it on potatoes and it was very good. At least, we feel like we reduced the amount of reseeding for the next year.