In a large wok, over medium high heat, stir fry the sweet potato slices and peanut oil for about 5 minutes.
Season with salt and pepper.
Reduce heat to minimum-low and cover for one minute before adding the sauce mixture.
In a small bowl, mix together all of the ingredients in the orange sauce.
Add sauce to the sweet potatoes and bring to a simmer.
Simmer and toss for an extra few minutes to let the sauce thicken a little.
Serve with the toasted walnuts and chopped green onions on top.