Place the sweet potato glass noodles in a bowl of warm water and soak for 20 minutes until they are soft and pliable.
Cut the chicken breast, potato, carrot, and onion into uniform 1-inch bite-sized pieces.
In a large pot or deep skillet, combine the water, tamari, coconut sugar, minced garlic, and grated ginger.
Add the chicken and potato chunks to the pot and bring the mixture to a boil over medium-high heat.
Reduce the heat to medium, cover the pot with a lid, and simmer for 15 minutes until the potatoes are nearly tender.
Drain the soaked noodles and add them to the pot along with the carrots and onions.
Continue to simmer uncovered for another 5 to 7 minutes, stirring occasionally, until the noodles are transparent and the sauce has thickened slightly.
Remove from heat and stir in the toasted sesame oil and black pepper.
Garnish with thinly sliced scallions and toasted sesame seeds before serving.