Preheat the oven to 400°F and prepare a baking sheet with parchment paper if needed.
Scrub the potatoes thoroughly under cold water, dry them well, then poke all over with a fork. Rub the skins with oil and sprinkle with salt before placing them in the oven to bake until tender and cooked through.
While the potatoes bake, cook the chopped bacon in a frying pan over medium heat until crispy. Remove and drain on paper towels.
Once the potatoes are done, allow them to cool slightly before cutting them in half lengthwise. Carefully scoop out the insides into a large bowl, leaving a thin layer inside the skins to keep their shape.
Add sour cream, milk, butter, salt, pepper, half the cheese, half the green onions, and the cooked bacon to the bowl. Mash everything together until creamy and well combined, adjusting the consistency with a little milk if needed.
Place the potato skins back onto a baking sheet and fill them generously with the mashed mixture. Sprinkle the remaining cheese and green onions on top.
Return the filled potatoes to the oven and bake until heated through and the cheese is melted and slightly golden.
Remove from the oven and serve warm.