Step 1
Preheat the oven to 275 degrees F (135 degrees C).
Step 2
Place black fungus in a large bowl and fill with water.
Step 3
Combine mirin 1/2 cup soy sauce 1/2 cup brown sugar 3 green onion bulbs chopped onion and garlic in an oven-safe pot over high heat. Bring to a boil.
Step 4
Place pork belly skin-side down on a flat work surface. Roll up lengthwise and wrap with butcher's twine. Place pork belly in the pot with the mirin mixture and partially cover with a lid.
Step 5
Bake in the preheated oven until pork is tender and an instant-read thermometer inserted into the center reads at least 145 degrees F (63 degrees C) about 4 hours.
Step 6
Bring a separate pot of water to a boil over high heat. Gently place eggs in the pot and cook until yolks are barely set 8 to 10 minutes. Transfer eggs to a bowl filled with ice water. Let sit about 1 minute. Remove from water and peel eggs.
Step 7
Place eggs in a container with 1 cup water 1/2 cup soy sauce and 2 tablespoons brown sugar. Dampen a paper towel in the mixture and use it to cover the container. Refrigerate 4 hours to overnight.
Step 8
Drain the fungus and add to the liquid in the pot with the pork belly. Cover with a lid and refrigerate 4 hours to overnight.
Step 9
Skim fungus from the top of the pork belly mixture and place in a pot with 8 cups water; fungus should be covered in pork belly fat. Add 1/4 cup soy sauce and miso paste. Bring to a boil.
Step 9
Remove skin from the pork belly using a knife. Chop the meat into pieces of desired thickness. Cut eggs in half lengthwise.