Prep the leaves: Gently rinse perilla leaves and pat dry well. Remove any tough end stems so the stack is neat and easy to layer.
Make the seasoning paste: In a bowl, mix gochugaru, garlic, green onions, soy sauce, fish sauce, sesame oil, sesame seeds, sugar, vinegar, and grated onion. The mixture should be thick but spreadable.
Taste and adjust: Dip a corner of a leaf and taste.
Add a pinch of sugar if it’s too sharp, more gochugaru for heat, or a splash of soy sauce for saltiness.
Layer and spread: Stack 5–6 leaves at a time. Spread about 1–2 teaspoons of paste on the top leaf, then place another leaf on top and repeat. Keep going until you’ve used all the leaves and paste.
Press and rest: Transfer the stack to an airtight container.
Press gently to distribute the seasoning. Let it rest for 30 minutes at room temperature to meld flavors.
Serve or chill: Enjoy right away for a fresh taste, or refrigerate for a few hours for deeper flavor. Serve with hot rice, grilled meats, or in lettuce wraps.