Cut potatoes into bite-sized pieces and soak in water. Drain well.

Slice cucumber into rounds and onion thinly.

Cut ham into 1cm strips and halve the carrot lengthwise, then slice thinly.

Rub cucumber and onion with salt (1/3 tsp) in a bowl, let sit for 10 minutes, rinse, and drain.

Microwave carrot in a heatproof container for 1 minute at 600W.

Boil potatoes in water until tender, about 10 minutes. Drain and return to the pot over medium-low heat to evaporate excess moisture.

Mash hot potatoes with vinegar and salt in a heatproof container. Let cool slightly.

Mix mashed potatoes with mayonnaise and salt and pepper in a bowl.