Crisped up kielbasa and a warm mustardy dressing make this a standout potato salad. Dressing the potatoes while warm helps soak up the flavors of the dressing, and the raw crunchy celery and fresh herbs perk up the whole dish.
Put the potatoes in a large pot and cover with water by a few inches; season with salt. Bring to a simmer and cook until tender, 8 to 10 minutes. Drain the potatoes.
Meanwhile, heat 2 tablespoons olive oil in a large skillet over medium-high heat. Add the kielbasa and cook, tossing, until well browned, 3 to 4 minutes. Add the red onion and cook until just wilted but still crunchy, 1 to 2 minutes. Reduce the heat to low and whisk in the vinegar and mustard. Whisk in the remaining 2 tablespoons olive oil until smooth; season with 1/2 teaspoon salt and a few grinds of pepper.
Transfer the hot potatoes to a large serving dish. Season the potatoes with 1 teaspoon salt, then pour the kielbasa mixture on top and gently toss. Add the celery, celery leaves, parsley and dill; toss. Serve warm.
Don’t throw away your celery leaves! Treat them like herbs and chop them up to use in salads, or toss them with potatoes like we did here.