Kimchi Filling
1-Cook the noodles: Cook the noodles. In a pot, heat water to a boil. Boil the noodles according to the package instructions until cooked. Drain and rinse with cold water. Then finely chop the noodles into small pieces.
2-Chop the kimchi: Chop the kimchi. Finely chop the kimchi and gently squeeze out excess liquid by hand.
3-Blanch the bean sprouts: Blanch the bean sprouts. Blanch the bean sprouts in boiling water for 1 minute. Drain and rinse the bean sprouts in cold water to stop them from cooking. Squeeze out any excess liquid and chop them into about 1/4-inch pieces
4-Drain the tofu: Drain the tofu. Using a cheesecloth, squeeze out the excess water from the tofu. It should be crumbled and broken up.
5-Combine: Combine. In a large mixing bowl, add the chopped dangmyeon noodles, chopped kimchi, chopped bean sprouts, drained tofu, diced yellow onion, chopped garlic chives, ground pork, garlic, ginger, sesame oil, soy sauce, sugar, salt and black pepper. Mix by hand until fully combined. It should look like a paste and be slightly sticky. If it is too dry and does not hold together, either add a little kimchi brine back in or add an egg. It should not be wet or runny.
6-Taste and adjust: Taste and adjust. Cook a teaspoon of filling in the microwave for 15-30 seconds and taste. Adjust the seasonings as needed.

Assemble
7-Wrap the dumpling: Wrap the dumpling. Place a dumpling wrapper in the palm of your hand and add about 1-2 tablespoons of filling in the center. Wet your finger and lightly wet the outer edge of the dumpling wrapper. Fold in half and completely seal the dumpling.
8-Create a half-moon shape: Create a half-moon shape. To create the half-moon shape, bring the two edge pieces together and seal by adding water and pinching tightly. Place the dumplings on a parchment-lined baking sheet and cover them with plastic wrap to prevent them from drying out while you finish assembling the rest of the dumplings.
9-Steam (option 1): Steam (option 1). Prepare your steamer, by boiling water over medium-high heat and lining your steamer basket with parchment paper. Place the mandu in the steamer leaving space between each piece to prevent them from touching. Cover and steam for 15 minutes.
10-Boil (option 2): Boil (option 2). Bring a pot of water to a boil over high heat. Carefully add the mandu in batches into the pot and boil in the water stirring periodically until they begin to float and then cook them for an additional 1-2 minutes or until done about 6 minutes total. Remove the kimchi dumplings with a spider strainer and serve immediately.