Make the crispy chicken skin:
Preheat oven to 200°C (fan 180°C).
Lay the chicken skin flat on a baking tray lined with baking paper. Sprinkle with a pinch of salt, cover with another piece of baking paper, then weigh down with a second tray.
Roast for 20 minutes until golden and crisp. Remove and set aside to cool.

Cook the chicken:
While the skin crisps, heat a splash of sesame oil in a saucepan over medium heat.
Add the chicken thighs and cook for 2–3 minutes each side until lightly browned. Remove and set aside (they’ll finish cooking in the broth).

Build the broth:
In the same pan, add the onion and cook gently for 5 minutes until softened.
Stir in garlic, ginger, and shiitake mushrooms. Cook for 2 minutes until fragrant.
Pour in the stock and bring to a simmer. Stir in the miso paste and soy sauce.

Finish the soup:
Return the chicken thighs to the pan and simmer gently for 12–15 minutes, until cooked through. Remove, shred with two forks, then stir the chicken back into the broth.
Cook the noodles separately according to packet instructions, then drain and divide between bowls.

Serve up:
Ladle the miso-shiitake broth and chicken over the noodles.