Place a rack in the center of your oven and preheat to 400°F. Grease a 9x13-inch baking dish with nonstick spray. Place a wire rack over a baking sheet.
Scrub and dry the potatoes. Prick them all over with a fork and rub them with the oil. Place on the wire rack over the baking sheet. Bake for 60 minutes, or until they pierce easily with a thin, sharp knife.
Meanwhile, heat a large skillet over medium-low heat. Add the bacon in a single layer and cook, turning the slices occasionally, until it is crispy and the fat is rendered, about 8 minutes. Transfer to a paper towel-lined plate.
When the potatoes are cooked, remove them from the oven and decrease the temperature to 350°F.
If you'd like to leave the skins on the potatoes (this gives the casserole a nice texture I personally like), once cool enough to handle, cut the potatoes into large pieces and place them in a large mixing bowl. If you prefer your potatoes to be peeled, half the potatoes lengthwise, then scoop out the flesh into a large mixing bowl.
Crumble the cooked bacon into small pieces and set 2 tablespoons aside for topping. Add the rest to the mixing bowl along with the butter, yogurt, milk, 1 cup cheddar cheese, all but 1 tablespoon of the chives, the paprika, onion powder, garlic powder, salt, and pepper.
With a potato masher or large fork, mash the potatoes until well mixed. There will still be some chunks, but that’s fine. Don’t overwork the potatoes or they’ll be gummy.
Transfer the potato mixture to the prepared baking dish and smooth it into an even layer. Top with the remaining 1/4 cup cheddar and reserved bacon.
Bake the twice baked potato casserole for 20 to 25 minutes, until the casserole is crispy on top and heated through. Let cool for 5 to 10 minutes, then top with the remaining chives and serve warm.
Notes
TO MAKE AHEAD: Assemble the casserole, cover and refrigerate for up to 2 days. Bake, covered, for 10 to 15 minutes at 350°F, then remove the cover and bake for 20 to 25 minutes. (Alternatively, you can bake the potatoes in advance, then cut them into pieces and warm them in the microwave before proceeding with the recipe.)
TO STORE: Refrigerate twice baked potato casserole wrapped in the dish or in an airtight storage container for up to 3 days.
TO REHEAT: Heat up leftovers in a 350°F oven until warmed through, or warm in the microwave.
TO FREEZE: Potatoes don’t freeze well (they get mealy!), so I don’t recommend freezing this recipe.