1. In a large mixing bowl, combine all-purpose flour and salt and gradually incorporate warm water to the flour mixture using your hands. Start with about ¾ cup of water and add more water as needed to form a soft, non-sticky dough.
2. Knead the dough on a floured surface for about 6-7 minutes until it becomes smooth and elastic. If the dough is too sticky, add a bit more flour. If it's too dry, add a little more water.
3. Divide the dough into 8 even pieces (roughly 20-25g each), and incorporate food coloring into each piece (2 white (no coloring), yellow, red, pink, green, blue, black). Form the dough into a ball, cover it with a damp cloth, and let it rest for at least 30 minutes. (While the dough rests, make the dumpling filling)
4. After resting the dough, select 2 colors and roll the dough out on a floured surface using a rolling pin to about a palm sized disk. Trim the edges of the circular disk to make an even square and repeat for the second color. Cut the square into even sized strips, then line them alternating with each color. Carefully using a rolling pin, roll the striped dough with even pressure until the dough is about 2mm thick. Using a cup or cookie cutter that’s 3-4 inches in diameter, cut out each dumpling skin. Repeat for each color.
5. If the dumpling wrappers will not be used immediately, cover the wrappers with a damp cloth and cover with food wrap to prevent them from drying out.
Mandu filling and folding
In a large mixing bowl, combine ground pork, mushrooms, chives, garlic and ginger, salt and pepper, and soy sauce. Mix until evenly incorporated.
1. Place 1 tablespoon of dumpling filling in the center of the wrapper. Dip your finger into a bowl of water and line the edge of the wrapper with water to moisten the edges.
2. Fold the wrapper in half into a taco shape. Press the top edges together and hold the mandu with your thumb and forefinger. Use your other hand to create pleats on one side of the wrapper.
3. Continue pleating along one side, pressing the pleats into the opposite smooth edge. Aim for 2-3 pleats on each side. Press the edges together for a final seal.