Step 1: Preheat your oven to 425°F (220°C). Lightly flour a baking sheet or line with parchment paper.
Step 2: In a large bowl, whisk together the 2 cups flour, baking powder, baking soda, and 1/2 teaspoon salt for the biscuits.
Step 3: Add the very cold, cubed butter to the dry ingredients. Use a pastry blender, two knives, or your fingertips to cut the butter into the flour until the mixture resembles coarse crumbs with some pea-sized pieces of butter remaining.
Step 4: Pour in the cold buttermilk. Stir gently with a fork just until the dough comes together. Be careful not to overmix; a shaggy dough is perfectly fine.
Step 5: Turn the dough out onto a lightly floured surface. Gently pat the dough into a 1-inch thick rectangle. Fold the dough in half, then pat it out again to 1-inch thick. Repeat this folding and patting process 2-3 more times to create layers. This is crucial for flaky biscuits.
Step 6: Use a 2.5-inch biscuit cutter (or a knife) to cut out biscuits. Do not twist the cutter, as this can seal the edges and prevent rising. Gather any scraps, gently pat them together, and cut out more biscuits. You should get 6-8 biscuits.
Step 7: Place the biscuits on the prepared baking sheet, ensuring they are slightly touching for softer sides, or spaced apart for crispier sides. Bake for 12-15 minutes, or until golden brown on top and bottom.
Step 8: While the biscuits bake, prepare the gravy. In a large skillet over medium-high heat, cook the bulk breakfast sausage, breaking it up with a spoon, until it's fully browned and no pink remains. Drain off all but 1/4 cup of the rendered fat.
Step 9: Reduce heat to medium. Sprinkle the 1/4 cup flour over the cooked sausage and fat. Cook, stirring constantly for 1-2 minutes, allowing the flour to cook out its raw taste and form a roux.
Step 10: Gradually pour in the warm whole milk, whisking continuously to prevent lumps. Continue to whisk until the gravy thickens to your desired consistency, about 5-7 minutes. It will thicken more as it cools.
Step 11: Season the gravy with 1/2 teaspoon black pepper and 1/4 teaspoon salt, or to taste. Keep warm until ready to serve.
Step 12: Once the biscuits are baked, split them open and generously smother them with the hot sausage gravy. Serve immediately and enjoy!