For the pancake batter: Sift together the cake flour, all-purpose flour and salt over a medium bowl. Stir in the canola oil and boiling water. Use your hands to work the dough into a smooth ball. It should be fairly firm. If it isn't, stir in some additional flour. Turn the dough onto a flat surface and flatten it with the palm of your hand until about 1-inch thick. Wrap in plastic wrap and allow it to rest in the fridge while you make the dressing and heat the oil.
For the vinaigrette: In a medium bowl, whisk together the soy sauce, sesame oil, red wine vinegar, ginger and garlic. Taste for seasoning.
To roll the dough: Lightly flour a flat surface and divide the dough into four parts. Use a rolling pin to roll out the first piece. When about 1/4-inch thick, sprinkle with scallions and fold the dough in half so the scallions are hidden inside. Roll thin again and cut into rounds using a glass (or round cookie cutter) about 2 inches in diameter. Transfer the rounds to a baking sheet fitted with parchment paper.
To cook and serve: In a large saute pan, heat 1/4-inch canola oil. Prepare a baking sheet fitted with a kitchen towel to drain the pancakes as they cook. When the oil smokes ever so slightly, use a pair of tongs or spoon to lower a few of the rounds into the oil. Fry for a minute on one side and then another on the second side. Use a slotted spoon or metal spatula to remove the pancakes and drain them on the kitchen towel. Sprinkle with remaining scallions and serve with the dressing on the side for dipping. Alternatively, drizzle the dressing over the pancakes. Serve immediately.
While I firmly believe most foods taste better after a few moments of sitting, this recipe is not. Fry them when everything else is ready and you are really ready to serve them.