Preheat oven to 180 C / 350 F.
Lightly spray a muffin tin with cooking spray. Set aside.
Place shrimp (prawns) in a bowl. Add sesame oil, Chinese five spice, soy sauce, oyster sauce and rice vinegar. Toss to coat. Set aside.
Top each nori sheet with 1 tablespoon of rice, and press into the muffin tin.
Top each with 1 shrimp.
Transfer to oven, and bake for about 20 minutes or until shrimp (prawns) is cooked through.
Carefully remove the baked cups from muffin tin and place in a serving platter.
Divide chopped cucumbers among the cups.
Sprinkle with sesame seeds and spring onions (scallions).
Drizzle with kewpie mayo. Serve hot.