Marinate the egg yolk
Place the egg yolk in a small container and gently pour over the light soy sauce and mirin.
Cover and refrigerate overnight, or for at least a few hours.
If you're short on time, you can also use a regular egg yolk.
Prep your toppings
Finely dice the onion and spring onions.
Cut the Spam into strips and set everything aside.
Make the sauce
Add the sugar, light soy sauce, Neoguri seasoning, olive oil, sesame oil and chicken powder to a bowl.
Mix well until everything is combined.
Glaze the Spam
Heat a little oil in a pan over medium heat.
Add the Spam pieces and fry until golden brown around the edges.
Add the sugar and soy sauce, then toss everything together until the Spam is sticky, caramelised and glossy.
Remove from the pan and set aside.
Cook the noodles
Bring a pot of water to a boil and cook the Neoguri noodles according to the packet instructions, usually around 5 minutes then drain well.
Toss the noodles
Add the cooked noodles to a bowl with the sauce.
Mix thoroughly until every noodle is coated in that savoury, glossy sauce.
Assemble
Top the noodles with the glazed Spam, diced onion, spring onion, crispy prawn katsu, strips of seaweed, sesame seeds and your soy-marinated egg yolk.
Give everything a good mix, break that yolk into the noodles and get slurping.