Heat a half cup of water in a microwave safe measuring cup.
Mix in 2 teaspoons kansui, using a spoon to ensure clumps are broken up.
Measure 240 grams of all purpose flour into a large mixing bowl. Pour in the kansui and use a wooden spoon to mix the water into the flour. Do NOT touch the kansui with your hands until it's all absorbed into the flour.
Once the kansui is absorbed in, then use your hands to briefly knead and shape the dough into a ball. The dough will not be smooth at this point. Wrap it in plastic wrap and let rest for 30 minutes. Immediately wash your hands!
After 30 minutes, unwrap the dough and knead for 3 minutes. Use a bench scraper to cut in half, return half of the dough to the plastic wrap.
Use your hands or a rolling pin to roll the dough to about ½" thickness.
*From here on out all instructions are for the KitchenAid pasta roller and press. Adjust directions accordingly if using another pasta roller.* Attach the pasta roller to the Kitchenaid. Turn to speed 2.
Pass the dough through the widest setting (1). Fold into thirds. It will be raggedy looking.
Repeat this pass and fold action 4-8 times, it will probably be closer to 8. Once the dough looks more supple and less raggedy, and is the width of the pasta roller, change the width setting to 2.
Run the pasta through at setting 2. Do NOT fold into thirds anymore.
Change the setting to 3, run the pasta through. Feel free to repeat any width again to ensure evenness. I used the bench scraper to cut the pasta sheets in half widthwise at this point.
Move the setting to 4. I stopped after 4 and set the dough aside.
Change the width back to 1 and repeat these steps with the other half of the dough.
Remove the pasta roller, and put on the spaghetti cutter. Turn the KitchenAid's speed to 7.
Run each sheet of dough through the spaghetti cutter. Divide each now cut sheet into about half and set aside in a little nest. Use a light touch here, do not mash the noodles together with any amount of pressure.
Repeat for all dough sheets until you have done them all.
Gently transfer the nests of noodles into airtight containers or put into boiling water immediately. Boil for 1 minute.