Japanese potato salad

Method

1. Put the sliced cucumber and onion in a bowl with the 5 g of salt. Toss and leave for 15 minutes while you cook the potatoes.
2. Put the potatoes in a pot, cover with cold water, salt the water well, and bring to a boil. Add the eggs to the same pot if you like, and lift them out after 11 minutes into cold water. Simmer the potatoes for about 15 minutes total, adding the carrot for the last 5 minutes, until a knife goes through a potato piece with no resistance.
3. Drain everything thoroughly. Return the potatoes and carrot to the dry pot and set it back over low heat for 30 seconds, shaking, until the surface steam has gone and the potatoes look chalky. Wet potatoes make a loose salad.
4. Mash the potatoes right there in the hot pot, but stop early. You want roughly half of it broken down and half still in recognizable lumps. Pour in the rice vinegar and grind in white pepper while everything is still steaming, and stir it through. Hot potato starch drinks the vinegar; cold potato does not, and you lose the acidity that makes this taste Japanese rather than bland.
5. Spread the potato out and let it cool to just barely warm, about 15 minutes. Mayonnaise stirred into hot potato splits and goes oily.
6. Squeeze the cucumber and onion hard in your hands, a small handful at a time, and discard the liquid. They should feel limp and almost dry.
7. Fold the cucumber, onion, chopped egg, and ham into the potato, then fold in the mayonnaise. Fold, do not beat, or the lumps disappear and you have mashed potato.
8. Taste for salt and pepper. Chill for at least 30 minutes before serving. It is better cold than warm.

Notes

• Kewpie mayonnaise is not the same product as European mayonnaise. It is made with egg yolks only rather than whole eggs, with rice vinegar rather than distilled vinegar, and the Japanese-made version contains MSG. The result is richer, less sharp, and savoury in a way ordinary mayonnaise is not.
• The German supermarket fix: whisk 15 ml rice vinegar and 6 g sugar into 120 g of ordinary mayonnaise, and use that as the 120 g in the recipe. This vinegar is separate from the 20 ml that goes onto the hot potatoes. Thomy Delikatess is a good base because it is already egg-yolk-forward. If you want to go further, add 1 g of MSG, sold in every Asia-Markt as Ajinomoto or simply “Geschmacksverstärker”.
• Or make the yolk-only version yourself: blend 2 egg yolks, 15 ml rice vinegar, 5 g sugar, 3 g fine salt, and 5 g mild mustard, then trickle in 200 ml neutral oil while the blender runs. That makes about 230 g, which is enough for this recipe with some left over. Keep it 3 days in the fridge.
• Buy the real thing if you can. Kewpie in the soft plastic bottle with the red cap is in every larger Asia-Markt in Germany and increasingly in the international shelf at Rewe and Edeka. The Japan-made bottle has Japanese text and the star-shaped nozzle; the EU-made one is milder.
• Salting and squeezing the cucumber is not optional. Skip it and the cucumber sheds water in the fridge overnight, the mayonnaise thins to a grey liquid, and the salad goes soupy by the next day.
• Use floury potatoes, not waxy. This is the opposite of what a German potato salad wants, and it is the point: floury potato collapses at the edges and thickens the dressing, which is where the texture comes from.
• Christoph already has Schwäbischer Kartoffelsalat on this site, which is the same vegetable handled in the exact opposite way: waxy potatoes kept whole in slices, warm broth and vinegar, no mayonnaise at all. Both salads dress the potato warm and for the same reason, and after that they part company completely. Serving them side by side at a summer table is a good argument.
• Add sweetcorn, sliced boiled sausage, or a spoonful of Japanese karashi mustard if you want. Some cooks add a little dashi powder for depth, which works.
• Keeps 3 days covered in the fridge. Do not freeze. Leftovers go into a sandwich with a slice of ham on soft white bread, which is how it usually ends up here.

Sources used

• Just One Cookbook: Japanese Potato Salad
• Japanese Cooking 101: Potato Salad
• No Recipes: Mom’s Japanese Potato Salad
• Sudachi Recipes: Japanese Potato Salad (Potesara)
• Just One Cookbook: Japanese Mayonnaise (Kewpie Mayo)