Bring a large pan of water to a simmer, then gently lower in the eggs. Simmer for 10 mins, then transfer to a bowl of iced water to cool. Meanwhile, finely slice the spring onions into long, thin strands, and add these to the ice water with the eggs. They will spiral and curl up in the cold.
Peel the eggs and cut them in half lengthways. Using a teaspoon, scoop the egg yolks into a bowl, and add the mayo, wasabi, sesame oil, vinegar from the ginger and some salt and pepper, and mash with a fork until smooth. For a smoother texture, blend using a stick blender until you get a pipeable mixture.
Put the furikake on a small plate and dip the egg halves, rounded-side down, into the seasoning so some sticks to the white of the egg. Pipe or spoon the egg yolk mix into the middles, then top with the pickled ginger. Pat the spring onion dry with kitchen paper, then use to decorate the eggs along with a pinch more furikake.