Preheat the oven to 180ºC
Place the potatoes on a baking tray, cover with 2 tbsps olive oil and 1 tbsp salt and cook for about 1 hour 15 minutes, or until cooked through and golden.
Remove from the oven and when they are cool enough to handle, cut them in half and scrape the flesh out of the potato skins, reserving it for the soup - leaving a little flesh inside the skins. Leave to cool completely.
Melt the butter in a large saucepan over a medium-low heat and cook the spring onion for 2 -3 minutes. Add the garlic clove, mustard, parmesan and stock and stir, then add the reserved potato flesh and bring to the boil, then cook for 15 minutes.
During this time, place the potato skins onto a clean baking sheet and sprinkle with the cheese, the chopped bacon rashers and a good grind of pepper. Place back into the oven to crisp up for 15 minutes until the cheese has melted.
When the soup has done cooking, purée until smooth with a stick blender or in a liquidiser.
Serve garnished with chopped chives and a good grinding of black pepper alongside the potato skins - use the potato skins for dipping!
Delicious with crumbled Wensleydale cheese and crispy bacon on the side.