Heat the oil and sauté the fish, garlic and root ginger for 3 to 4 minutes.
Meanwhile place the spinach in a large saucepan with 1 to 2 tablespoons water, cover and cook for 2 to 3 minutes, shaking the pan from time to time until the spinach has wilted. Add the sorrel with the Flora ProActiv spread and stir through.
Mix all the ingredients for the sauce in a saucepan and heat through gently.
Serve the crayfish on a bed of spinach and sorrel, topped with the sauce.