Create marinade by combining soy sauce, water, dried chili pepper, ginger, apple, dried kelp, onion, garlic, and rice syrup in a heavy pot. Cover and bring it to a boil over medium high heat for 20 minutes, until boiling.

Turn down the heat to low and keep boiling the marinade for another hour.

Let the marinade cool down a little bit, strain it, and then let it cool down thoroughly. Set aside.

Add prawns with chilled marinade