Cut the spring onion into rings, reserve 2 tbsp of green ring for garnishing. Preheat to 180C/350F.
Heat the oil in a large skillet. Add in the remaining chopped spring onions. Cook briefly. Add in drained Nameko mushrooms and cook for 2-3 minutes. Add in chopped kale and cooking cream, cooking until everything is heated through. Season with salt and pepper. Transfer to a baking form.
Rinse and pat the code fillets dry with a paper towel. Sprinkle with lemon juice and coat with cornstarch seasoned with salt and pepper. Place them on the top of vegetables and bake in the middle of hot over for about 20 minutes. Remove and vanish with reserved spring onions.