Cook the potatoes. Rinse them, then put in a big pot with cold water to cover. Salt and bring to a boil over high heat. Reduce heat to a vigorous simmer and cook until potatoes can be pierced easily with a sharp knife.

While potatoes are cooking, sauté bacon until crisp in a large skillet, then transfer to a paper towel-lined plate to drain. Prepare the dressing, combining mayonnaise, yogurt, olive oil, kimchi pickling juice, black pepper and 1 teaspoon salt in a bowl.

Assemble the potato salad. When potatoes are just tender, drain and place in a large bowl. Let them cool slightly, maybe 5 minutes. Add dressing and stir gently with a rubber spatula or wooden spoon to coat potatoes. Add most of the scallions, reserving a handful of the green tops, the kimchi and the bacon. Stir gently until just combined. Taste and adjust seasonings as needed. Transfer to a serving bowl and top with reserved scallion greens. Serve warm, at room temperature or chilled.