Preheat the oven to 200°C (400°F). Lightly grease a baking sheet.
Cream together the cream cheese, spring onion or chives, garlic powder, and crabmeat or crabsticks; chill for 20 minutes.
Lay out the wonton wrappers in a single layer on the baking sheet. Put about 1/2 tablespoon of the cream cheese mixture in the centre of each wonton.
In a small bowl, whisk together the egg and water until foamy. Dip your fingers in the egg wash and use the same fingers to pinch together the corners of each wonton to seal the cream cheese inside.
Spray the wontons with olive oil and bake using the top and bottom heat + fan function for 8 to15 minutes until the edges turn golden brown.
Prepare the Homemade Sweet and Sour Sauce. Whisk together the sugar, vinegar, oyster sauce, garlic powder, onion powder, and ketchup in a medium-sized saucepan over medium-high heat. Bring to a boil.
In a small bowl, whisk together the cornstarch and water until dissolved then pour into the sauce and stir until thick. Set the heat to lowest setting until wontons are ready to serve.