In a small bowl, soak 1/2 cup sliced onion in water to cover about 10 minutes to temper their bite; drain.
In a large pot with a lid, toast the star anise and cinnamon stick over medium, stirring occasionally, until very fragrant, about 2 minutes. Add the remaining sliced onion and the ginger. Cook, stirring occasionally, until fragrant, about 1 minute. Add 15 cups water, the turkey parts, the vegetables and 2/3 cup cilantro. Partially cover and bring to a simmer over high. Uncover, reduce the heat to medium-low and let simmer, skimming off any foam, until the flavors infuse and meld, about 1 hour 15 minutes; let broth rest 10 minutes.
Remove the turkey pieces and rinse with cold water. When cool enough to handle, shred the meat into bite-size pieces and transfer to a bowl. (Discard the bones, cartilage and skin.)
Set a fine-mesh strainer over a large bowl (line with cheesecloth for extra-clear broth). Strain the broth, discarding any solids, then return to the pot. Stir in 3 tbsp. fish sauce, adding the remaining 1 tsp. to taste if needed; season with salt and pepper.
In a large pot of boiling water, cook the noodles according to the package directions; drain well.
Meanwhile, in a small bowl, whisk the cranberry sauce and the sriracha until smooth.
Bring the broth to a boil over high. Divide the noodles among 6 bowls. Top with the turkey meat, scallions, remaining 1/3 cup cilantro and the soaked onions. Ladle the broth into the bowls; top with the mint. Serve the pho with the sriracha-cranberry sauce.
