Preheat the oven to 425 degrees F (220 degrees C).

Dice 4 of the shiitakes and halve 8 of them. Soak in hot water for 30 minutes to rehydrate. Meanwhile, soak noodles in cold water for 15 minutes.

Arrange kabocha squash on a baking pan. Add some water to the pan.

Roast in the preheated oven until tender, about 15 minutes.

Drain noodles and chop into small pieces. Mix noodles, diced shiitakes, turkey, fish sauce, and white pepper thoroughly using a fork. Mixing thoroughly will make the meatballs chewy and delicious.

Bring water and chicken stock to a boil in a large stockpot. Shape turkey mixture into egg-shaped balls, or quenelles, using 2 hot, wet spoons. Drop meatballs into the boiling broth. Cook until they float, 10 to 30 seconds.

Peel skin off the squash if desired. Dice into 1 1/2-inch pieces. Drop into the soup with the halved shiitakes and shrimp. Cook until shrimp is opaque, about 5 minutes more.

Taste and add more fish sauce if desired. Top with scallions, cilantro, and black pepper.