Samgyupsal Gui (Grilled Pork Belly)

Name: Samgyupsal Gui (Grilled Pork Belly)
Cuisine: Korean
Ingredients: 1 pound sliced fresh pork belly (samgyupsal, 삼겹살); 8 cloves garlic, thinly sliced; 4 green chili peppers, roughly sliced; 3 - 4 scallions, thinly sliced (or pa muchim); 2 to 4 ounces mushroom caps - white, crimini, or king mushrooms - optional; 4 chili peppers - optional; 2 heads of red or green lettuce; 16 perilla leaves, kkaennip (깻잎) - optional; 1 tablespoon sesame oil; 1/2 teaspoon salt; black pepper to taste; 2 tablespoons doenjang 된장 (Korean soybean paste); 1 tablespoon gochujang 고추장 (Korean red chili pepper paste); 1 teaspoon minced garlic; 2 teaspoons sesame oil; 1 teaspoon sesame seeds; 1 tablespoon rice wine or mirin - optional (If the sauce is too thick, use a tablespoon of water to thin it.)