Mix all of the filling ingredients together in a large bowl with your hands or a wooden spoon. Cover and refrigerate for 30 minutes to let the flavours incorporate together.
Remove filling mixture from the fridge and let it sit for 10 minutes before wrapping.
Dust a little flour on your fingers and place a mandu wrapper on your palm. Add 2-3 spoons of the filling to the center. Dab a little water along the edges of the wrapper. Seal tightly into a half-moon shape. Dab a bit more water on the two ends, and stick them together to create a round shape. PRESS TIGHTLY. Repeat this process for the rest. (You can also freeze the mandu in a plastic bag/container for use later).
Place mandu in a steamer and steam over high heat for 10-15 minutes.
Mix the dipping sauce ingredients together. Dip mandu in the sauce and enjoy!