Place sugar in a sauce pan over medium heat and cook until it turns into a thick caramel, about 10-15 minutes. But watch carefully as it will go from perfect to ruined in the blink of an eye
Mix the fish sauce, lime juice, chili sauce, and garlic and carefully add it into the caramel. The caramel will likely seize up but continue to heat and slowly stir until it dissolves and the fish sauce mixture is completely incorporated.
Remove from the heat and let the mixture cool.
Marinate the chicken wings in the sauce for 30 minutes to overnight. The longer - the better in my view.
Preheat your oven to 400F/200C.
Remove wings from marinade and set aside. Place the chicken wings on a rack, on a foil lined baking sheet (you'll thank me for this step later - lol). Bake about 25-30 minutes or until golden brown and crispy.
Take the reserved marinade, put it in a sauce pan and simmer over medium heat until it becomes thick and syrupy, about 7-10 minutes. NOTE: Because you brought it to a boil for a sustained amount of time, it is safe.
Toss the wings in the caramel sauce. Pile them on a plate and top with the chopped scallions and sesame seeds. ENJOY!!!