In a large bowl, combine ground pork, kimchi, shredded onion, garlic, ginger, soy sauce, rice wine (if using), egg, sesame oil, salt, and pepper. Mix well.

Place a dumpling wrapper in the palm of your hand and add a teaspoon of the filling in the center. Moisten the edges with water, fold over, and pinch to seal.

Heat 1 tablespoon of vegetable oil in a pan over medium heat. Arrange dumplings in a single layer and cook until bottoms are golden brown.

Add cold water to the pan and cover immediately to steam the dumplings for about 10 minutes.

Remove lid and cook until water has evaporated, adding remaining vegetable oil if needed.

Serve hot, garnished with black sesame seeds and green onions.