In a bowl, combine soy sauce, mirin, brown sugar, grated ginger, minced garlic, sesame oil, and black pepper. Whisk until sugar dissolves and ingredients are well blended.

Marinate

Place the pork slices in a shallow dish or zip-top bag and pour the marinade over them, turning to coat all pieces. Marinate at room temperature for 20–30 minutes (or refrigerate up to 2 hours for deeper flavor). If refrigerating, bring to room temperature 15 minutes before cooking.

Cooking & Garnish

Heat pan

Heat a large skillet or cast-iron pan over medium-high heat until hot. Add the neutral oil and swirl to coat the surface.

Sear pork

Remove pork from the marinade, letting excess drip back into the bowl. Reserve the marinade for step 5. Arrange slices in a single layer in the hot pan without overcrowding (work in batches if needed). Sear 2–3 minutes per side until nicely browned and edges start to caramelize. Pork belly will render fat; tilt the pan occasionally and spoon rendered fat over the slices to baste.

Finish with marinade

After both sides are seared and pork is nearly cooked through (internal temperature about 145°F / 63°C), pour the reserved marinade into the pan and bring to a simmer. Cook 1–2 minutes, spooning the glaze over the pork until slightly reduced and sticky. If using gochujang or chili flakes, whisk a small amount into the marinade before adding for a spicy glaze.

Rest and garnish

Transfer the pork slices to a serving plate and let rest 2–3 minutes. Sprinkle with thinly sliced scallions and toasted sesame seeds. If desired, spoon any remaining glossy pan sauce over the pork.

Serving suggestion

Serve warm as an appetizer or over steamed rice with pickled vegetables or a simple salad.