Make the marinade by whisking together all the ingredients. Set aside.
Prep the oyster mushrooms by pulling them apart into smaller pieces--about the size of real chicken wings or chicken thighs. Then, pour the marinade over the mushrooms. Using your hands, toss the mushrooms so they are evenly coated with the marinade. Then, place them in an airtight container and into the refrigerator for at least 30 minutes and up to 4 hours.
While the mushrooms are marinating, prepare the dredge by whisking together Korean tempura flour mix, corn starch, sugar, onion powder, garlic powder, white pepper, and black pepper in one large bowl.
Then, take 1/2 cup of the dredge and place in a separate bowl. To this second bowl, whisk in about 3 to 4 tablespoons of soju--whatever is needed to reach a pancake batter like consistency.
Bring your frying oil up to 375° F. When your oil is at temperature, coat the marinated mushroom pieces first in the dry dredge, then in the wet batter, and then once more in the dry dredge, before dropping in the oil. Make sure not to crowd the pan, as this will significantly lower the temperature of the oil.
Cook the mushroom pieces until they are golden brown (about 3 minutes), flipping as necessary. Remove and place on a cooling rack to drain excess oil. Finish cooking the rest of the oyster mushrooms and allow them to cool to room temperature.
While your vegan fried chicken is cooling, make the sauces. First, combine all the ingredients for the soy glaze by whisking them together in a small bowl or liquid measuring cup.
Pour the contents into a small pot over low to medium heat until it comes to a boil (around 3 minutes), stirring regularly. Once it reaches a boil, continue stirring but lower the heat to the lowest possible setting. Keep stirring until the sauce thickens into a glaze. Remove from heat and set aside.
For the Sweet & Spicy Sauce, simply whisk together all the ingredients and set aside.
Once the vegan fried chicken has cooled to room temperature, bring your frying oil up to 400° F. Then, add the vegan fried chicken to your oil and cook for about 1 minute. Remove and set aside on the cooling rack for about 5 minutes.
Set aside 1/3 of the vegan fried chicken--these will remain unsauced. Place another third in a deep bowl, together with the Soy Glaze. Toss until they are evenly coated.
Finally, use a brush to coat the remaining third of the vegan fried chicken with the Sweet & Spicy Sauce.
Garnish with sesame seeds and scallion greens before serving.