Start by finely chopping the ginger, garlic, and green onions. Slice your mushrooms and the pork belly meat into very fine slices and then cut each slice into 2-inch pieces.
Into a hot pot on medium heat drizzled with oil, add the garlic and ginger. Stir them till they brown a bit, for 1-2 minutes.
Stir in the pork belly till they lose the pink color and cook.
Add your liquids, the mirin, soy sauce, and chicken broth.
Let them boil after covering the pot with a lid, then lower the temperature, uncover the lid and let it simmer for 10 minutes.
Add in your green onions and mushrooms, then raise the heat again and let it boil.
Let it simmer on low heat till the mushrooms are soft, then add in your sesame oil and vinegar with a sprinkle of salt and pepper to taste. Remove the pot from the heat and set it aside.