Peel the potato and cut into thin slices, they should look like french fries. Use a mandolin slicer if you have it. Put the shredded potato into a bowl of cold water. Set aside for at least 10 minutes.
Heat oil in a wok or a medium size skillet. Add the peppers and cook on medium high heat for 2~3 minutes or until crisp tender.
Add the scallion and cook for 1 minute.
Squish the potatoes around in the water and drain all of the water.
Put the drained potatoes in the pan and cook on medium-high heat, stirring frequently until the potatoes are tender but not mushy. This will take about 3~5 minutes.
Add the vinegar and soy sauce (if using); mix well. Season with salt and pepper. Serve hot or at room temperature.