Preheat your oven to 180ºC/350ºF/gas 4. Prick the potatoes and pop them straight on a shelf in the oven for 1½ to 2 hours, or until cooked through. Leave to cool on a wire rack.
Chop the bacon into small pieces. Heat a little oil in a large pan and sauté the bacon until crispy and golden. Tip into a mixing bowl.
Halve the potatoes lengthways and scoop out the centre, leaving a 5mm edge. Add half of the potato flesh to the bowl (save the rest for another dish).
Grate all of the cheese and finely chop the chives. Add one third of the the Cheddar and most of the chives to a bowl, then season with sea salt and black pepper and mash everything together.
Place the potato skins on a baking tray. Add a spoonful of filling to each one, then make a well for the eggs to go into. Crack in the eggs, sprinkle over the remaining cheese and bake for 12 minutes, until the egg is cooked but still soft. Top with the remaining chives.