Place the potatoes in a large saucepan with a lid and add

cold water to cover and a generous seasoning of salt. Cover,

place over high heat, and bring to a simmer. Reduce the heat

to medium to maintain the simmer and cook, uncovered,

until the potatoes are tender and a sharp knife slides easily

in, about 15 minutes.

While the potatoes are cooking, make the dressing: Mix

together the sour cream, horseradish, mustard, lemon juice,

and onion in a medium-size bowl. Season generously with

salt and pepper. Or see the Fork in the Road for a

classic creamy dressing.

Drain the potato quarters well and let them sit until they

are cool enough to handle. Cut them into ½-inch dice. While

they are still slightly warm, toss them in a large serving bowl

with the dressing. Serve at room temperature.