Preheat the oven to 225 degrees Celsius. Line a baking sheet with aluminium foil and set aside.
Using a fork or a skewer, poke holes all around the potato to release the steam generated during baking. Rub olive oil all over the potato and place it on the lined baking sheet. Bake for 60 minutes until a fork can be inserted into the potato with little resistance.
Remove the potatoes and reduce the heat to 200 degrees Celsius. Melt 1 ½ tablespoons butter.
Using tongs / clean kitchen towel, cut 2 potatoes into half lengthwise. Scoop out the potato flesh of 4 potato halves, leaving a thin layer of potato in the potato shell. Place them back on the baking tray, brush the insides with the melted butter and bake at 200 degrees Celsius for 10 minutes. Turn the potatoes over, brush with more melted butter and bake for another 10 minutes until the shells are hard. Remove the potato shells from the oven and set aside.
Reduce the oven heat to 190 degrees Celsius.
While the potatoes are baking, place a frying pan on medium heat. Add in the bacon fry until browned and crispy. Remove from heat onto paper towels to drain. Once cool enough to handle, crumble the bacon into small bits. Reserve 1 tablespoon of the bacon fat and discard the rest.
Heat the reserved bacon fat over medium-low heat. Add in the chopped onion and stir-fry until the softened. Remove from heat and let cool.
Scoop out all the flesh of the remaining 1 potato and discard the skin. Combine the potato flesh together with the remaining 1 ½ tablespoons softened butter, bacon, onion and ½ cup of cheese. Season well with salt and pepper. Scoop the potato filling back to the potato shells and bake for 10 to 15 minutes until warmed throughout. Top with the remaining ¼ cup of cheese and bake until the cheese has melted (and golden brown if desired).