Preheat the oven to 425 degrees F. Butter a Dutch oven or cast iron skillet.

In a medium bowl, combine the flours, baking powder, sugar and salt.

Grate the butter in and stir to combine. With your hands or a spoon, work in the bacon grease.

Fold in the buttermilk. Flour your hands and lightly knead the dough into a ball. The dough should be moist but not sticky. Add flour and/or buttermilk, if needed.

Pinch off about 8 equal pieces and form into a biscuit. Place the biscuits in the Dutch oven or skillet. Bake for about 30 minutes, or until lightly browned and the internal temperature is 190 - 200 degrees F. Let rest until warm, before removing and serving.