Preheat grill to medium-high. Line an oven tray with foil, then spray with vegetable oil. Rinse the rice until the water runs clear. Put in a small saucepan with 250ml (1 cup) water, cover and bring to a simmer over medium heat. Reduce heat to low and cook for 12 mins or until tender and the water is absorbed. Turn off heat and stand, covered, for at least 5 mins. Fluff rice with a fork.
Step 2 — Prep fish
Meanwhile, thinly slice the spring onion. Put 3 tsp kecap manis in a shallow bowl. Pat the fish dry with paper towel. Dip the flesh side of the fish in the kecap manis, then put on the centre of the lined tray, skin-side down, and scatter with the sesame seeds.
Step 3 — Make sauce
Combine the remaining kecap manis, 2 tsp soy sauce, 1 tsp white vinegar and 2 tsp water in a bowl.
Step 4 — Grill fish and veggies
Scatter the stir-fry vegetables around the fish on the tray. Spray the fish and veggies with vegetable oil. Drizzle the veggies with the sauce mixture and season with salt and pepper. Grill for 7-8 mins until the veggies are tender and the fish is cooked through (see Kitchen 101).
Step 5 — Serve up
Divide the rice, fish and veggies among plates. Drizzle with the tray juices, scatter over the spring onion and enjoy!
Step 6 — Kitchen 101
Cooking time may vary depending on the thickness of the fillets. To test the fish, flake with a fork; if it comes apart easily, it is cooked.