- Heat oven to 200C/180C fan/gas 6. Prick the potatoes all over with a fork, then rub with half the oil, some sea salt and black pepper. Arrange on a baking tray and bake in the oven for about 1 hr 15 mins, until their skins are crisp and they are completely tender when prodded. Meanwhile, heat the remaining oil and half the butter in a frying pan.
- Add the onion and gently cook for 15-20 mins until softened and golden. Remove from the pan and set aside, add the chopped bacon and fry until just crisp.
- Remove using a slotted spoon and place on kitchen paper.
- Halve each potato lengthways (watch out, they will be hot), then scoop out most of the potato into a bowl, leaving a potato skin shell with a thin layer of potato.
- In the bowl, crush the potato with the remaining butter and the double cream. Season with salt and pepper. Fold through the onion, bacon, three-quarters of the cheeses and half the parsley. Spoon back into the potato shells and top with the remaining cheese.
- Transfer to the baking tray and return to the oven for 10-15 mins, until melting and golden.
- Sprinkle with the remaining parsley and serve with a sharply dressed crisp salad, if you like.