Wash and peel all potatoes. Cut 1 pound into 1-inch cubes, place in a pot of water, and bring to a boil over high heat. Boil for 10-12 minutes or until fork-tender. Drain and mash until smooth. Let cool slightly.

Meanwhile, grate the remaining potatoes using the large holes of a box grater. Immediately place grated potatoes in a bowl of cold water and let sit for 5 minutes to prevent discoloration. Drain well, then squeeze in a clean kitchen towel to remove excess liquid.

In a large mixing bowl, combine the mashed and grated potatoes. In a separate bowl, whisk together the flour, baking powder, salt, and pepper. Gradually add the flour mixture to the potatoes, stirring gently.

Slowly add the buttermilk, stirring until a thick, scoopable batter forms (similar to drop biscuit dough).

In a large skillet, heat 1 tablespoon oil and ½ tablespoon butter over medium heat until shimmering but not smoking.

Working in batches, spoon batter into the skillet, spacing each pancake at least 1 inch apart. Using the back of a fork, flatten to about 3-4 inches wide, shaping into circles.

Cook 3-4 minutes per side or until golden brown and crispy. Flip and cook another 3-4 minutes. Place on a paper towel-lined plate. Repeat with remaining batter, adding more oil and butter as needed.

Serve warm, topped with sour cream and green onions.