1. Toss the cucumber,onion and carrot in a little salt and stand for 15 minutes. Rinse off the salt under running water and dry on paper towel. Bring a small saucepan of water to the boil and boil the eggs for 8 minutes. Transfer the egg into iced water to stop the cooking. Peel and roughly chop.
2. Boil a kettle of water and pour over the broccolini in a heatproof bowl or tray. Stand for a minute or so,then remove from the water,roughly chop and season with salt.
3. Cut the potatoes in half,place in a large pot,cover with cold water and bring to a simmer. Simmer for 25 minutes or so until the potatoes are very tender. Allow to cool,then cut in half and slip the skins off the potatoes. Roughly mash,seasoning with salt and the vinegar.
4. While the potatoes are still slightly warm,add the mayonnaise,cucumber,carrot,spring onion,spinach, broccolini,egg and spinach to the potato and mix together. Season well with salt again. Taste and adjust the seasoning if needed. This dish can be served warm,at room temperature,or chilled.
Also trymy original Japanese-style potato salad