1. Preheat the oven to 400°F (200°C). Scrub the russet potatoes well and pat them completely dry. Pierce each potato several times with a fork, then rub all over with olive oil and a pinch of kosher salt.

2. Place the potatoes directly on the oven rack or on a baking sheet and bake for 45 to 55 minutes, or until the potatoes are tender when pierced with a knife. Let cool for 10 to 15 minutes, until comfortable to handle.

3. Slice each potato in half lengthwise to create long boat shapes. Using a spoon, gently scoop out the flesh into a mixing bowl, leaving about 0.25 inch of potato attached to the skins so they stay sturdy. Arrange the empty shells cut side up on a baking sheet.

4. Brush the insides and edges of the potato shells with a little more olive oil and season lightly with salt and black pepper. Return the tray to the 400°F oven and bake for 8 to 10 minutes, until the skins are golden and crisp around the edges.

5. While the shells crisp, add the melted butter, milk or half and half, sour cream, garlic powder, remaining salt, and remaining pepper to the warm potato in the bowl. Mash until mostly smooth and creamy.

6. Stir 1 cup of the shredded cheddar cheese and all of the shredded mozzarella into the mashed potatoes until the cheese is melted and evenly distributed. Taste and adjust seasoning if needed.

7. Spoon the cheesy potato mixture back into each crisped shell, mounding it slightly. Sprinkle the tops with the remaining 0.5 cup shredded cheddar cheese and most of the crumbled bacon, reserving a little for garnish.

8. Return the stuffed potato skins to the oven and bake for 10 to 12 minutes, until the cheese is melted, bubbling, and lightly browned in spots.

9. Remove from the oven and let cool for a few minutes. Top with the remaining bacon and sliced green onions. Serve warm with extra sour cream on the side for dipping.