Place half the potatoes into a large microwave-safe bowl and add 1/4 cup water. Cover with a microwave-safe plastic lid or vented microwave-safe plastic wrap

Select SMART COOK POTATO setting and turn the AMOUNT dial to 1kg. Press START button

Pause cooking program to stir halfway through. Press START button to continue cooking program

Remove and set aside in a large serving bowl and repeat with remaining potato

Toss through onion and vinegar; set aside to cool

Combine dill, sour cream and mayonnaise together and season with mustard, salt and pepper

Gently fold through cooled cooked potatoes

Serve either room temperature or cold