Place a heavy-bottomed pot or Dutch oven over medium heat and add the sliced pork belly.
Cook the pork belly until the fat has rendered and the edges are golden and crispy.
Add the chopped kimchi, minced garlic, and grated ginger to the pot, sautéing for 3 to 5 minutes until the kimchi softens and becomes fragrant.
Stir in the gochujang and sesame oil, ensuring the pork and vegetables are evenly coated in the spice paste.
Pour in the beef bone broth and bring the liquid to a gentle boil.
Carefully add the cubed firm tofu to the pot and reduce the heat to low.
Simmer the stew for 10 to 12 minutes to allow the tofu to absorb the smoky and spicy flavors of the broth.
Season with sea salt and black pepper to taste.
Ladle the stew into a bowl and garnish with freshly sliced green onions before serving.