Preheat oven to 425°F (220°C).
Roast the Potatoes: Toss cubed potatoes with olive oil, 1 teaspoon salt, and 1/2 teaspoon pepper on a baking sheet. Spread in a single layer. Roast for 25-30 minutes, flipping halfway, until golden brown and crispy on edges with a fork-tender center.
Cook the Bacon: While potatoes roast, cook bacon in a large skillet over medium heat until very crispy, 6-8 minutes. Transfer to a paper towel-lined plate to drain and cool; crumble. Reserve 1/4 cup of rendered bacon fat.
Make the Dressing: In a large mixing bowl, whisk together sour cream, Greek yogurt, remaining 1/2 teaspoon salt, and remaining 1/4 teaspoon pepper. Slowly drizzle in the warm reserved bacon fat while whisking constantly to emulsify.
Assemble the Salad: Add hot roasted potatoes to the bowl of dressing. Toss gently to coat. Add shredded cheddar, crumbled bacon, and half the chives. Fold together just until combined.
Finish & Serve: Taste and adjust seasoning. Transfer to a serving bowl and top with reserved chives and extra cheese. Serve warm, at room temperature, or chilled.