Japanese Potato Salad (very good)

adapted from chowhound https://greatist.com/eat/best-japanese-potato-salad & just one cookbook https://www.justonecookbook.com/japanese-potato-salad/

4 to 5 medium Yukon Gold potatoes, peeled and quartered
1/3 cup Kewpie (Japanese) mayonnaise
1/2 cucumber (preferably Japanese or English) thinly sliced
1/4 red onion, thinly sliced
1/2 carrot, peeled and thinly sliced

1 oz ham, thinly sliced

1 egg, hard-boiled and diced
Extra sea salt for salting & blanching vegetables

Seasoning:
1/3 teaspoon freshly ground black pepper
1 teaspoon sea salt
1 tablespoon rice vinegar
1 tablespoon sugar
1/2 teaspoon karashi, Japanese spicy mustard

1. Put the potatoes in a saucepan of cold, salted water so the water is just covering the top of the potatoes. Bring to a simmer. Cook the potatoes until a chopstick poked into them goes in without resistance, about 15 minutes. Drain the potatoes in a colander.

2. While Potatoes are cooking prepare the other vegetables: Sprinkle both onion slices and cucumber slices lightly with sea salt, and mix with your hands making sure the salt coats them evenly. Set aside for 10 minutes. After 10 minutes rinse off vegetables in a colander and wrap and gently squeeze vegetables in a clean dishcloth or a few paper towels to get all of the moisture out. This is a very important step and will prevent soggy potato salad.

3. Place the cooked potatoes into a medium-sized bowl and gently smash with a fork or potato masher making sure you leave some small chunks. In a small bowl mix together the seasoning ingredients and pour over the potatoes, gently tossing to evenly coat the potatoes. Add the onions, cucumber, carrots, egg, ham, and Kewpie Mayonnaise, and gently combine with the potato mixture until all of the ingredients are combined. Serve at room temperature or chilled in the refrigerator.