Place the minced garlic, sugar, chili flakes, Sichuan pepper powder, Chinese five-spice powder, and chicken stock powder into a medium bowl.
Heat the chili oil and vegetable oil in a small saucepan over medium heat until hot but not smoking.
Carefully pour the hot oil over the garlic and spice mixture. Stir gently as the mixture becomes fragrant.
Whisk in the soy sauce, rice vinegar, and hot water until combined. Set aside while cooking the wontons.
Bring a large pot of water to a rolling boil.
Add the wontons and cook until they float. Fresh wontons usually take about 4 minutes, while frozen wontons require 6–8 minutes.
Remove the wontons using a slotted spoon and transfer them to serving bowls.
Spoon the prepared sauce generously over the wontons.
Garnish with chopped green onions and drizzle with additional chili oil if desired.
Serve the Spicy Wontons in Chilli Sauce immediately while hot.