Heat 1 tablespoon neutral oil in a large pot over medium-high heat. Add the onion and cook for 5 minutes. Add the sweet potato and sauté for 5 minutes.
Sprinkle the dashi granules over the sweet potato and onion and toss to coat. Cook for 1–2 minutes.
Simmer the broth:
Pour in the chicken broth and bring to a boil. Reduce the heat to low and add the zucchini and shredded chicken. Simmer for 25 minutes or until the sweet potatoes are fork-tender.
Make the miso mixture:
Combine the white miso paste, tamari, mirin, sesame oil, chili oil, tahini, and hot water in a bowl. Whisk until completely smooth. Set aside.
Cook the noodles:
While the broth is simmering, bring a medium pot of water to a boil. Cook the noodles according to the package directions. Drain, rinse, and divide among four bowls.
Finish the ramen:
Turn off the heat on the broth. Add the miso mixture and all but a pinch of the scallions. Let stand for 5 minutes. Taste and adjust the seasonings as needed.
To serve:
Ladle the broth over the cooked noodles. Serve with the remaining minced scallions on top. Enjoy!