Substitute ribeye steak with sirloin or rump steak.
In a saucepan, add the stock, ginger, garlic, spring onions, chili, soy sauce and mirin.
Stir, cover and bring to the boil over a medium high heat. Lower the heat to medium and let it simmer for 20 minutes.
In the meantime, grill the steak in a smoking hot pan with sesame seed oil, turning to cook for 3 minutes on each side.
Leave the meat to rest for half its cooking time. Slice into slivers and sprinkle with chilli flakes.
Strain the stock to remove the spring onions and chilli, then return to the saucepan.
Add the mushrooms, carrots, pak choi and noodles to the broth and cook noodles according to the package timing instructions, about 3 minutes.
Evenly divide the hot stock and noodles between the two bowls and top with slices of ribeye steak, pak choi greens, carrots, soft boiled eggs and any other toppings you like. Garnish with spring onions, sesame seeds and enjoy!