Preheat the oven to 350°F. Line a baking tray with parchment paper.
Place the potatoes on the baking tray, poke holes in them with a fork, and drizzle with the olive oil. Bake for approximately 1 hour, or until fork-tender.
While the potatoes are baking, fry the bacon in a hot skillet for 2 to 3 minutes per side. Chop up roughly and set aside.
Once the potatoes are done, allow them to cool briefly for approximately 15 minutes. Carefully cut off the top third of each cooled potato lengthwise. With a spoon, gently scoop out the fluffy flesh and put it into a mixing bowl.
Mash the potato with a masher or a fork until smooth. Add the butter, sour cream, milk, and salt and pepper to taste. Mix all the ingredients until well combined.
Add the crispy bacon, spring onions, and half of the grated cheddar cheese to the bowl of mashed potatoes.
Generously fill each potato skin. Sprinkle the remaining cheddar cheese over each potato. Set the oven to BROIL (or you can use a grill) and heat the potatoes for 2 to 3 minutes, or until the cheese is melted.