Preheat the oven to 200⁰c.
Peel and cut the potatoes into ¾ inch chunks. In a large bowl toss together the potatoes, 2 tbsp of the oil and 1 tsp salt and the black pepper.
Spread out into a single layer on a large baking tray and roast, stirring once halfway through, until browned and cooked through, about 25-30 minutes. Remove from the oven and let cool slightly.
While the potatoes are roasting, heat the remaining oil in a frying pan on a medium heat. Add the shallots and the remaining salt. Cook for about 5-7 minutes, stirring occasionally, until softened and brown. Add the garlic and cook for a further 2 minutes. Remove from the heat.
In a large bowl, stir together the sour cream, mustard, and red wine vinegar. Add the cooked potatoes, shallots and garlic and gently toss to coat.
Taste for seasoning and stir through the parsley. The salad can be served warm or at room temperature.