Heat a splash of oil or a few sprays of light cooking spray in a medium saucepan over medium high heat. Add garlic and ginger and cook for 3 minutes, stirring regularly to make sure it doesn’t catch.
Add mirin, soy sauce and stock to the saucepan. Stir well and bring to a light simmer. Leave for around 15–20 minutes.
Meanwhile, place egg in a small saucepan of cool water. Place over high heat, bring to the boil and then cook for 4 minutes. Immediately plunge into a bowl of ice cold water after.
Lay chicken breast on a chopping board and cover with clingfilm. Very lightly beat with a rolling pin to flatten a little. Season with sea salt and black pepper. Heat a frying pan or skillet over a medium high heat with a drizzle of olive oil or a few sprays of cooking spray. Once hot, add chicken breast and cook for 4 minutes, then turn and cook for another 4 minutes. Remove from heat, cover with foil and leave to rest for at least 5 minutes.
Cook noodles according to packet instructions. For the last 30 seconds of cooking, drop the pak choy into the boiling water. Drain both the noodles and pak choy and separate. Meanwhile, peel and halve the eggs and slice the chicken breast.
Remove stock mixture from the heat. Take around 1/2 cup of it in a bowl and whisk in miso to dissolve and mix well.
Place noodles in a bowl and pour over the miso stock mixture. Top with egg halves, sliced chicken breast, pak choy and spring onion. Finish with some finely ground black pepper.