(Cook’s Illustrated, modified by Sarah)
1 russet potato (about 8 oz.), scrubbed, dried, poked a few times with a fork, and rubbed lightly with vegetable oil
1 oz. sharp cheddar cheese, shredded (about 1/4 cup)
2 Tbsp sour cream
2 Tbsp buttermilk
1/2 Tbsp unsalted butter, room temperature
1 medium scallion, sliced thin
Salt and pepper, to taste
Adjust oven rack to upper middle position and heat oven to 400 degrees. Bake potato for 1 hour. Cool potato for 10 minutes on a wire rack.
Cut potato in half and scoop out the innards into a bowl. Put the potato skins back in the oven. Meanwhile, mash potato flesh with fork until smooth. Stir in remaining ingredients, until well combined.
Remove shells from oven. Spoon mixture into crisped shells, mounding slightly at the center, and return to oven. Bake until spotty brown and crisp on top, 10 to 15 minutes. (If you’re impatient, you can broil them instead.)