Start by placing the potatoes in a large pot and covering them with water. Bring them to a boil and cook over medium-high heat for 20 to 40 minutes, depending on the size of the potatoes. Test them for doneness by poking with a knife—the blade should slide in easily. Once tender, drain the potatoes and rinse them under cold water to cool slightly. While still warm, peel off the skins and slice the potatoes into ⅛ to ¼-inch (3 to 6 mm) pieces. Transfer them into a large serving bowl.

While the potatoes are cooking, melt the butter (or oil) in a medium saucepan over medium heat. Add the diced bacon and onions, sautéing them until the bacon renders its fat and the onions become soft and translucent—about 5 to 7 minutes. Stir in the broth and bring the mixture to a simmer. Once simmering, remove the saucepan from the heat and mix in the vinegar, mustard, salt, pepper, and celery seeds.

Pour the hot dressing over the warm, sliced potatoes and stir gently to coat. Let the salad rest at room temperature for 20 to 30 minutes to allow the potatoes to absorb the flavors.

After resting, give the salad a gentle stir and taste for seasoning. Adjust the flavor by adding sugar, salt, pepper, vinegar, or mustard as needed. Just before serving, sprinkle the freshly chopped chives on top for a burst of color and freshness.