Rinse off the fresh or thawed pieces of oxtail and cook in salted boiling water for 5 minutes. Drain the water, rinse the tail pieces again and dry them well. Fry brown in sunflower oil. Lift out of the oil with a slotted spoon. Put the water, the mushroom broth, the cinnamon stick, the lemon juice and the soy sauces in a casserole with a lid and simmer for 3 hours. Peel and chop the onion. Roast in the remaining oil until light brown and add to the broth along with the oil.
In the meantime, to garnish, wash the fresh celery, shake dry and pluck and chop the flawless leaves. Use two teaspoons of it immediately and freeze the remaining leaves. Measure frozen goods and allow to thaw. Cut the flawless stems crosswise into approx. 3mm wide rolls and freeze unused goods in portions. Clean the remaining ingredients up to the celery stalks, cut into small pieces and immediately add to the stock.
Strain the broth after 2.5 hours and return it to the casserole. Let the material to be sieved cool to lukewarm. Press the garlic cloves into the broth. Cut off the substrate and the mycelium at the bottom of the Shimeji mushrooms. Separate the stems close to the hat and cut into small pieces. Have mushroom hats and stems ready.
Separate the meat from the bones and keep them ready, discard the bones. Remove the cinnamon stick and kaffir lime leaves. Put the remaining material to be sieved into the pot and puree it finely with a magic wand. Season the broth with salt and black pepper. Add the meat and simmer for another 30 minutes. 10 minutes before the end, stir in the coconut milk and add the mushrooms. Mix the rice wine with the tapioca flour and stir in 5 minutes before the end. Distribute the finished soup on the serving bowls, garnish, serve immediately and enjoy warm.