In a large bowl, combine the ground pork, scallions, ginger, garlic rice vinegar, mirin, soy sauce and salt. Use your hands to mix all the ingredients thoroughly together. Set aside.
Fill a small bowl with water. Lay a wonton or dumpling wrapper on a clean work surface and scoop about 2 teaspoons of the filling into the center of the wrapper. Dip your finger in the water and paint all around the edge of the wrapper to moisten.
Option 1: Fold the wrapper over in half to look like a half-moon, press and seal. Repeat.
Option 2, Gather the wrapper at the top and press together to make a “purse”. Repeat.
Heat 2 tbsp of the oil in a large nonstick skillet over medium heat. Once the oil is shimmering, add as many dumplings that can fit in a single layer, flat side down, then cook until golden brown, 2 to 3 minutes.
Carefully pour in ½ cup water and IMMEDIATELY cover with a tight-fitting lid and reduce the heat to low, so that you don’t get burned by the popping water.
Cook until almost all the water has evaporated, the dough is tender and shiny and the filling is cooked through, about 5-6 minutes.
Remove the lid, then continue to cook until all the remaining water has evaporated, and the bottom of the dumplings crisp up again, 1 to 2 minutes more.
Repeat the process one more time until all the dumplings are cooked.
Serve with your favorite soy-sauce based dipping sauce.