Teriyaki Beef Donburi

Name: Teriyaki Beef Donburi
Ingredients: 250 g white/wild rice blend, precooked and set aside,; 160 g medallion beef steak,; 1 tbsp decent Teriyaki sauce, I used Lee Kum Lee brand,; Half a carrot, cut into very thin long batons,; Half a green bell pepper, cut into thin long batons,; Half a Pak choi, very ends of white stalks trimmed off,; Half a red chilli cut into thin rings, seeds removed,; 1 spring onion, chopped finely,; 1 tsp nigella seeds, (to garnish),; 1 tbsp light soy sauce,; Salt to season,; 1 dash water, plus a bowl of cold water,; 1 tbsp cornflour; Spray coconut oil