Place the soy, mirin, brown sugar, vegetable oil, sesame oil and ginger in a bowl and mix to combine.
Divide marinade in half.
Add prawns to one half and refrigerate for 30 minutes.
Add rice wine vinegar and sesame seeds to the remaining marinade to make sesame dressing and set aside.
Thread prawns onto skewers.
Heat a bbq or grill pan over high heat. Cook skewers in batches for 2-3 minutes each side or until just cooked.
Coat each quarter of avocado in sesame seeds.
Place shallots, radish, ginger and baby herbs in a bowl and toss to combine.
Serve skewers with sesame avocado, radish salad and sesame dressing.