Clean, wash and cut the leek into rings. Heat 2 tablespoons of oil. Steam leek, remove. Fry the rice in the frying fat, deglaze with broth. Let it swell for about 20 minutes at low heat.
Wash the fish, cut it into pieces, sprinkle with lemon juice and let it steep a little. Dab fish pieces dry with kitchen paper, salt and fry in the remaining hot oil for about 5 minutes. Keep warm.
Add 5 tablespoons of water, soy sauce, ketchup and vinegar. Stir starch with a little cold water until smooth and thicken the sauce with it. Bring to the boil again. Season to taste with salt and pepper.
Fold the leek into the rice, put it on plates and arrange the fish pieces on top. Cover the fish with sauce. Serve garnished with halved lemon slices.