Place potatoes in a large pot and cover with cold water by about an inch. Add a generous pinch of salt.

Bring to a boil over medium-high heat, then reduce to a simmer. Cook until potatoes are tender when pierced with a fork, about 15–20 minutes depending on size.

Drain the potatoes in a colander and let them cool just enough to handle. Dice into 1-inch pieces.

In a medium bowl, whisk together sour cream, mayonnaise, Dijon mustard, and a pinch each of salt and freshly ground black pepper. Taste and adjust seasoning.

In a large bowl, combine the warm diced potatoes, chopped green onions, and crumbled bacon.

Pour the dressing over the potato mixture and gently fold to combine. Adjust seasoning and add reserved potato cooking water or extra sour cream if the potato salad seems dry.

Garnish with additional green onions, paprika, or parsley. Serve at room temperature or chilled.