Preheat oven to 450°F.
Drizzle 2 tablespoons of the bacon fat on a sheet pan. Add the tender sweet potatoes and toss to coat lightly. Use a knife to score the skin then use a potato masher or the bottom of a measuring cup to smash the sweet potatoes so that some of the inside protrude from the skins and they are relatively flat, but still hold together.
Drizzle the remaining bacon fat evenly over the tops of the smashed sweet potatoes and bake in the hot oven until crisp and caramelized around the edges, about 18 to 22 minutes.
Use a flexible spatula to transfer the sweet potatoes to a serving dish, garnish with the crumbled bleu cheese and the minced chives.