Preheat oven to 200°C. Drizzle the potatoes with oil and rub with salt. Bake until cooked through – about an hour and fifteen minutes. If using smaller potatoes, cook for about 45 minutes.
Cool for ten minutes and slice the potatoes in half. Scoop flesh from the skin, being careful not to break the skin, and place the potato into a bowl. Add crème fraiche, butter, garlic and chives to the potato and mix together. Refill the skins with the cheese and potato mixture.
Bake potatoes for about 15-20 minutes, until they begin to brown. If using new potatoes, bake for 5-10 minutes. Sprinkle with blue cheese and chopped chives and serve.