For filling: Combine soy sauce, cornstarch, curry powder, sesame oil and sugar in a mixing bowl. Finely chop slaw. Add slaw, chicken and onion to curry mixture; mix well. Cover and chill for 1 hour or up to 24 hours.
Spoon 2 teaspoons filling onto each wrapper. Moisten edges with water. Fold wrappers in half over filling. (For wontons, fold one corner over filling to opposite corner). Fold pleats along edges and press to seal.
Arrange potstickers, pleated edges up, on a lightly floured baking sheet, pressing gently to fatten bottoms. Cover until read to cook.
Heat 2 tbsp cooking oil in a 12-inch skillet. Arrange half of the pot stickers, pleated edges up, in skillet. Cook, uncovered over medium heat for 1-2 minutes or til bottoms are light brown. Reduce heat to low.
Remove from heat; carefully add 2/3 cup water all at once near edge (oil may splatter). Return to heat. Cover and cook 10 minutes more. Increase heat to medium-high. Uncover; cook 3-5 minutes or til filling is no longer pink and water is evaporated.
Add 2 teaspoons oil. Lift and tilt skillet to coat potsticker bottoms. Cook uncovered 1 minute more. Gently remove potstickers from skillet. Drain on paper towels. Keep warm in a 300 degree F oven. Repeat with remaining potstickers.
To make ahead: Cover uncooked potstickers on cookie sheet and refrigerate up to 1 day. Or, place potstickers in a shallow freezer container with a tight-fitting lid. Freeze up to 2 weeks. Let thaw 30 minutes before cooking.