Step 1 Soak skewers in cold water for 20 minutes. Place prawns, olive oil and chilli flakes (if using) in a medium bowl; toss to coat. Thread prawns onto skewers and set aside for 5 minutes.
Step 2 Bring a medium saucepan of water to the boil. Immerse snow peas to blanch until just tender. Refresh in cold water, drain well and transfer to a large bowl.
Step 3 Use a vegetable peeler to cut long ribbons from cucumbers and carrot, stopping at cucumber seeds. Add cucumber, carrot and beans to snow-pea bowl to make salad. Whisk soy sauce, mirin and sesame oil in a small bowl; add to salad and lightly toss.
Step 4 Preheat a grill pan or barbecue hotplate to high. Grill reserved prawn skewers for 2 minutes per side, or until lightly charred and just cooked through.
Step 5 Sprinkle skewers with sesame seeds and serve with salad.