How to Make It
Cook the bacon in a large Dutch oven over medium until crisp, about 10 minutes. Remove, reserving 2 tablespoons of the drippings in the Dutch oven. Add the potatoes, parsnips, leeks, garlic, and salt and cook, stirring often, until slightly tender, about 10 minutes. Stir in the broth and water and bring to a boil over medium-high. Reduce heat to medium-low; cover and simmer 15 minutes.
Working in batches, process the potato mixture in a blender until smooth. Stir in the cream and vinegar. Top with the bacon and scallions.