In a large bowl, combine the ground chicken, onion soup mix, sesame oil, minced garlic, chopped cilantro, oyster sauce, and nonfat milk; mix thoroughly until well combined.
Arrange 12 gyoza wrappers on a baking sheet or clean counter. Divide half of the filling into 12 equal portions and place each portion in the center of a wrapper.
Brush the edges of each wrapper with the egg white beaters and seal by crimping in half to form a potsticker or pinch the edges up to form a purse. Repeat with the remaining 12 wrappers and filling to make 24 potstickers total.
Heat a large nonstick skillet over high heat and spray lightly with nonstick cooking spray. Place as many potstickers as fit in a single layer without touching.
Cook uncovered for 2 minutes to brown the bottoms, then add 3/4 cup water to the pan and immediately cover to steam. Reduce heat as needed so the water sizzles and steams the dumplings.
Keep the pan covered until the water has evaporated, about 4 minutes. Remove the lid and continue cooking about 1 more minute until the bottoms are crisp and golden.
Remove the potstickers from the pan and serve hot with your preferred dumpling/gyoza dipping sauce.
