- Heat oven to 375°F. Pierce potatoes in several spots with a fork. Place directly on center oven rack. Bake about 45 minutes or until very tender. Transfer to a wire rack; cool 10 minutes.
- While potatoes bake, cook bacon in a small skillet over moderate heat, stirring occasionally, until browned and crisp, 5 to 8 minutes. Using a slotted spoon, transfer bacon to a paper towel–lined plate to drain. Reserve fat in skillet.
- If necessary, use oven mitts to hold a hot potato. Cut off top quarter of the potato. Using a spoon, scoop out potato, leaving a 1/4-inch-thick shell; transfer flesh to a bowl. Repeat with remaining potatoes. Mash potato in bowl until smooth. Mix in crème fraîche, half-and-half, scallions and 1½ tablespoons bacon fat from the skillet. Gently fold in all but 2 tablespoons of the chopped bacon (reserve the remaining for garnish). Season with kosher salt and pepper.
- Brush the outsides of the potato shells with some of the reserved bacon fat. Spoon or pipe potato mixture into shells. Place on a small baking pan. Bake until heated through and tops are beginning to brown, about 30 minutes.
- To serve, transfer the baked potatoes to a platter. Garnish with the remaining bacon and chopped chives.
Note: Potatoes can be baked and filled then covered loosely with plastic wrap, and chilled for up to 24 hours. Bake at 375°F until heated through, about 45 minutes.