Preheat the oven to 180 degrees Celsius.
In an oven proof pan with a lid, heat the olive oil and add the leeks and chopped dill. Saute for 4 - 5 minutes. Reserve 2 tablespoons of the fish stock and add the rest to the pan with the beans.
Mix the reserved fish sauce into the kudzu to form a paste.
Stir the kudzu paste into the pan.
Wipe the flathead fillets with a damp paper cloth and lay them on top of the leek and bean sauce.
Cover the pan with a lid and place in the oven to cook for 12 - 15 minutes
While the fish is cooking, steam the broccoli for 5 - 7 minutes until it's tender.
Note: Kudzu, like ginger is a tuber and can be used as a thickener for sauces. Being alkaline, the Japanese use it for medicinal purposes to help settle the stomach and promote digestion. It is a white chalk like substance and can be found in health food stores.
Makes 2 servings