Trim off the tougher ends of the garlic scapes.
Cut the scapes into 2-inch pieces then rinse and drain.
Soak dried shitake mushroom and dried kelp in ¼ cup of lukewarm water until soft. This should take about 10 to 20 minutes.
Set the mushroom aside.
In a large saucepan, combine the soy sauce, rice vinegar, onion, garlic, and ginger along with the soaked shitake, kelp, and its soaking water.
Bring the mixture to a boil then remove it from heat.
Pour the mixture over the garlic scapes.
Let the scapes cool down to room temperature.
Store the garlic scapes in an airtight container in the fridge.