In a large pot or Dutch oven, heat a thin layer of oil over medium heat. Once hot, add the pork belly pieces and cook until starting to turn golden brown, about 10 minutes.
Add the beef, crumbling as it browns. Once mostly browned, about 3–4 minutes, push the meats to the side of the pot and add the mushrooms. Cook the mushrooms until browned and glossy, about 3–4 minutes longer.
Add the carrots, onion, and garlic and stir to combine. Cook until fragrant, about 2 minutes.
Add the tomatoes, beef stock, and coconut aminos. Stir to combine and bring to a simmer. Turn the heat to medium low and simmer, covered, for 2 hours. Beef stock will reduce; if needed, add more beef stock to avoid burning.
Once ready, pork will be completely tender and tomatoes will have broken down. Divide into bowls and garnish with scallions and sesame seeds.