Cook the potatoes:

Place whole potatoes in a large pot and cover with cold water. Add a generous pinch of salt.

Bring to a boil and simmer for 15–20 minutes, until fork-tender. Drain and let cool slightly, then slice into ¼-inch rounds or chunks.

Cook the bacon:

In a skillet over medium heat, cook chopped bacon until crispy. Remove with a slotted spoon and set aside, leaving the drippings in the pan.

Make the warm dressing:

Add chopped onion to the bacon drippings and sauté for 2–3 minutes until softened.

Stir in vinegar, sugar, and Dijon mustard. Simmer for 1–2 minutes, scraping the bottom of the pan. Season with salt and pepper.

Assemble the salad:

Add warm sliced potatoes to a large bowl. Pour the hot dressing over the potatoes and gently toss to coat.

Add crispy bacon and chopped parsley, if using. Taste and adjust seasoning.

Serve warm:

Best served warm or at room temperature—not chilled.