Marinade chicken wings in salt & sugar mixture for at least 1 hour (maximum 6 hours).
Line your steamer with coffee filters or parchment papers to prevent chicken wings stick to the bottom.
Set up a steamer. Arrange chicken wings, about an inch apart, in a steamer. Depend on how big your steamer is, you might need to divide the wings into multiple batches.
Steam the chicken for approximately 30 minutes on medium high heat. Don't let the water touch the wings when boiling.
Arrange fully steamed chicken wings, 1 inch apart, nicely on a cooking tray (lined with parchment paper). Then chill them in the fridge for at least 2 hours.
The chicken wings need to be completely chilled and dried before proceed to next steps.
Take the wings out of the fridge and leave at room temperature for 15 minutes.
In a shallow pan/pot, heat enough vegetable oil on medium high heat. Make sure the oil reaches 350F before adding chicken to the pot.
Fry chicken into small batches, 5 minutes for each batch or until the skin is crispy and turns golden brown color.
In a large mixing bowl, toss chicken wings with sweet and spicy sauce. Garnish with scallion oil (if desired). Serve hot immediately.