Heat oil in a large sauté pan or wok over medium heat until shimmering. Add pork and cook, without moving, for 2 minutes; season with salt and pepper. Using a wooden spoon, break up pork and continue to cook until very browned and crispy, 5 more minutes. Using a slotted spoon, transfer pork to a bowl; reserve drippings in pan.
Meanwhile, pat tofu dry with paper towels or clean kitchen towel. Cut into ½-inch cubes and set aside.
Increase heat to medium-high. Add garlic, ginger, and serrano; cook, stirring frequently until garlic is lightly toasted, about 2 minutes.
Add mushrooms, bell pepper, onion, scallions, ½ teaspoon salt, and ½ teaspoon pepper. Cook, stirring frequently, until vegetables start to soften, 5 minutes.
Meanwhile, whisk together broth, gochujang, tamari (or soy sauce), honey, and fish sauce until smooth. Add cornstarch and whisk to combine. Add sauce to pan and cook 1 minute.
Decrease heat to low and add tofu and pork; cook to warm through, about 2 minutes.
Off heat, stir in sesame oil. Top with sesame seeds and serve with cooked rice.