How to Make It
Preheat oven to 500°F. Place potatoes in a large saucepan, and add water to cover by 1 inch. Season with 1 tablespoon salt, and bring to a boil over high. Reduce heat to medium, and simmer until potatoes are tender, about 10 minutes. Drain potatoes and let stand until cool enough to handle.
While potatoes cool, place beef fat in a small saucepan; cook over medium-low, stirring often, until rendered to about 1/2 cup melted fat, 15 to 20 minutes. Pour through a fine wire-mesh strainer into a bowl; discard solids.
Arrange potatoes on a rimmed baking sheet. Place a second rimmed baking sheet on potatoes, rimmed side up, and press down gently to crush potatoes without breaking them apart. Drizzle potatoes with half of the melted beef fat; turn potatoes to coat.
Roast potatoes in preheated oven until bottoms are golden, about 15 minutes. Remove from oven, and drizzle with remaining melted beef fat; turn potatoes to coat. Return to oven, and roast at 500°F until crispy and golden brown, 25 to 30 minutes.
Transfer potatoes to a large bowl. Sprinkle with vinegar, chili powder, garlic powder, hot paprika, sweet paprika, onion powder, and remaining 1 tablespoon salt; toss to combine. Place potatoes on a platter, and top with chives.