Peel the potatoes and cut into small chunks. Boil for 10 minutes. Check if the potatoes are cooked by inserting a skewer. If it goes through, the potato is cooked.
While the potatoes are being cooked, chop the onion and carrot into small pieces then put them on a plate, cover with plastic wrap and microwave for 2 minutes on 500w and set aside.*1
Cut the ham and apple into small pieces. Slice the cucumber thinly.
Combine the 3 tablespoons mayonnaise and 1 tablespoon milk. Set it aside.
Turn the heat off and drain the water from the potatoes, put them back in the pot and shake them around to rough up the outsides a little.
Mash the potatoes a little, but ensure you leave some potato chunks still in shape. *2
Place the mashed potato, onion, carrot, apple, cucumber, and ham into a bowl and add the mayonnaise mixture and mix to combine. *3
Season with salt and black pepper to taste then serve.
Notes
*1. Cooking the onion in the microwave brings out the onion’s sweetness.*2. Mash while the potatoes while they are still hot because the pectin layer containing the potato starch is more elastic when it is hot. If you mash the potatoes after they’ve cooled down, the pectin layer loses its elasticity and starchiness which results in a mashed potato texture like “mochi” (a texture which is opposite to “hoku hoku”).*3. Add the mayonnaise mixture while the mashed potatoes are cooled down to about 120-140°F (50-60°C). Mayonnaise penetrates better at around that temperature and also stops the mayonnaise from separating.