Pat the pork belly chunks dry and place in a large pot of cold water. Bring to a boil over high heat and boil for 3 to 5 minutes until white foam rises. Drain and rinse the pork under cold running water.

Fill the pot with 8 cups of fresh water and bring to a simmer. Add 6 smashed garlic cloves, sliced ginger, dried shiitake mushrooms, halved onion, 1 tablespoon doenjang, 1/4 cup rice wine, and 1 teaspoon sea salt. Stir to dissolve the paste and simmer for 2 to 3 minutes.

Return the blanched pork to the simmering broth, ensuring it is mostly submerged in liquid.

Increase heat to bring the pot to a rolling boil, then immediately reduce heat to low to maintain a gentle simmer.

Cover the pot slightly ajar and braise on low heat for 2 hours and 45 minutes without lifting the lid.

After 2 hours and 45 minutes, remove one piece and pierce with a fork; if it does not shred easily, continue simmering up to an additional 30 minutes. The internal temperature should reach 190°F.

Meanwhile, arrange lettuce or cabbage leaves, sliced jalapeños, thin-sliced garlic, and perilla leaves on a serving platter. Place ssamjang in a small bowl.

Remove the pork with tongs, let cool slightly, then slice against the grain into 1/4-inch thick pieces. Arrange on a platter and drizzle with some hot broth to keep moist before serving.