2 pounds Yukon Gold or yellow potatoes, unpeeled
1/2 pound bacon
1 large white onion, chopped
2 tablespoons expeller-pressed canola oil
3 tablespoons whole-grain mustard
6 tablespoons cider vinegar, or to taste
1 bunch green onions, chopped
1/2 teaspoon fine sea salt
1/2 teaspoon ground black pepper
2 tablespoons chopped fresh parsley
Place potatoes in a large pot of water and bring to a boil. Cook until just tender, about 15 to 20 minutes. Drain and cool slightly, then peel if desired and slice into thick rounds.
Meanwhile, cook bacon in a large skillet over medium heat until crisp; transfer to a paper towel-lined plate to let drain. When cool enough to handle, crumble into small pieces. Drain off all but 1 tablespoon fat from the skillet, then return to medium heat. Add white onion and cook until lightly browned, 7 to 8 minutes.
In a large bowl, gently toss together warm bacon, potatoes and white onion with oil, mustard, vinegar, green onions, salt and pepper. Garnish with parsley and serve warm or at room temperature.