Make the miso sauce
Place the miso, sugar, mirin, and sake in a medium pot and whisk until smooth. Place the pot over medium heat and bring it to a simmer.
Cook the mixture, stirring constantly, for 4 to 5 minutes. Add the lemon juice and cook for 8 minutes, stirring occasionally. Turn off the heat, add the red pepper flakes, and stir.
Make the chicken wings
Separate the chicken wings at the joints and dispose of the outer sections. Combine the onion powder, salt, egg, sake, cornstarch, flour, and 1 Tbs. of the ginger juice in a large bowl. Add the wings, coat with the mixture, and let stand for 20 minutes.
In another large bowl, combine 1/4 cup of the spicy miso sauce, vinegar, soy sauce, paprika, and the remaining 1 Tbs. ginger juice. Cut the scallion into very thin slices diagonally and set aside.
Heat 3 inches of the canola oil in a wok or deep skillet to 330°F. Add the wings in 2 batches and cook them for 6 minutes, turning them from time to time. Transfer the wings to a wire rack set over a baking sheet. Increase the heat of the oil to 350°F. Return the wings in 3 batches to the hot oil and cook them for 1 minute, or until the outside is crisp. Remove the wings from the oil and drain on the wire rack.
While the wings are hot, toss all of the cooked wings in the spicy miso sauce mixture until well coated. Transfer the chicken wings to a large platter. Garnish with the scallion and serve.
Transfer the leftover spicy miso sauce to a clean freezer container. Cover the jar with a lid and store it in the freezer.