In a large bowl, combine mirin, salt, and black pepper. Add the pork shoulder and make sure it's fully submerged. Cover and refrigerate for at least 4 hours or overnight.

Cooking the Pork

Preheat the oven to 300°F (150°C). Remove the pork from the brine and pat dry. Place it in a roasting pan and cook for about 3 hours, or until the pork is tender. Let it rest for 20 minutes before slicing.

Making the Scallion Pancakes

Prepare the Dough

In a bowl, mix flour and hot water until a dough forms. Knead until smooth, about 5 minutes. Cover and let it rest for 30 minutes.

Form the Pancakes

Roll the dough into a thin sheet, brush with oil, sprinkle with salt and scallions. Roll it up, coil it, and flatten into a pancake.

Cooking the Pancakes

Heat vegetable oil in a skillet over medium heat. Fry the pancakes until golden and crispy, about 3-4 minutes on each side. Keep warm.

Making the Dipping Sauce

Combine Ingredients

In a small bowl, mix together soy sauce, rice vinegar, sesame oil, and chili flakes. Adjust seasoning to taste.