Add self-rising flour and cold butter to the large bowl. Press butter into the flour using a pastry blender or a fork until it turns into a crumb consistency. Then, slowly pour cold buttermilk in a few additions. Mix using a spatula after each addition. Dough should be shaggy. Don't add the remaining buttermilk if the dough is already shaggy.
Dust a work surface with all-purpose flour and place the dough on it. Sprinkle with a little amount of flour and shape the dough into a disc. Then, flip the dough, add more flour if needed, and shape into the bigger disc (the size should be similar or a little smaller than the bottom of a cast iron skillet).
Melt the bacon grease in a 9-inch cast iron skillet over medium-high heat. Then, transfer the disc of the dough to the skillet. Reduce the heat to low. Cover with a lid and cook until the bottom of the homemade biscuit bread browned. Then, turn it over (add a 1 tbsp of melted butter, if needed). Cover and cook until golden brown on the other side. Enjoy with jam, butter, honey or maple syrup.