Begin by soaking 4 dried shiitake mushrooms in hot water for 30 minutes until they're soft and plump. Keep the soaking liquid - you'll use it later for extra flavor.
Take your 500g pork tenderloin and slice it very thinly. Cover the slices with plastic wrap and gently pound them with a kitchen mallet until they're about ¼ inch thick. This makes the meat tender and helps it cook quickly.
In a large bowl, mix together 2 tablespoons Chinese cooking wine, 1 tablespoon light soy sauce, ½ teaspoon baking soda, 2 minced garlic cloves, and a pinch each of salt and pepper. Add your pork slices to this marinade and let them rest for 30 minutes in the refrigerator.
After marinating, take each piece of pork and coat it with cornstarch. Shake off any excess and set aside.
Pour 4 cups of beef stock into a large pot. Add the soaked mushrooms, their soaking liquid, and a splash of soy sauce. Bring this to a boil over medium heat (175°C/350°F), then reduce to a simmer for 2 minutes.
Now drop the cornstarch-coated pork pieces into the simmering broth one at a time to prevent them from sticking together.
In a small bowl, mix ½ cup tapioca starch with ½ cup cold water until smooth. While stirring the soup constantly, slowly pour in this mixture a little at a time until the soup reaches your desired thickness. Keep the heat low to maintain a gentle simmer (82°C/180°F).
Beat 1-2 eggs in a bowl. While stirring the soup in one direction, slowly pour in the beaten eggs to create delicate strands.
Finally, season your soup with a few drops of sesame oil and salt to taste. Ladle into bowls and top with chopped spring onions.
Serve hot, either on its own or with steamed rice. If you'd like to make Maki Mi, simply add cooked fresh egg noodles to your bowl before pouring in the hot soup.
For best results, serve immediately while the soup is hot and the meat is at its most tender. Remember to stir your soup gently before serving to mix all the ingredients evenly.