1. Preheat oven to 375°. Stir together bacon drippings and butter.
2. Place flour in a large bowl. Stir in drippings mixture and buttermilk, stirring just until a dough forms.
3. Turn dough out onto a well-floured surface. Knead twice. Divide dough into 8 equal portions. Pat each portion into a 31⁄2-inch round biscuit (about 3⁄4 inch thick). Arrange 2 inches apart on a parchment paper-lined baking sheet.
4. Bake at 375° for 30 minutes or until tops are very lightly browned. Meanwhile, prepare Tomato Gravy. Serve biscuits immediately with Tomato Gravy.