Mix Dry Ingredients & Cut Butter: Preheat oven to 450°F (230°C). Line a heavy baking sheet with parchment paper. In a large bowl, whisk together flour, baking powder, baking soda, salt, and sugar. Add the cold cubed butter and cut in using a pastry blender or your fingertips until the mixture resembles coarse meal with pea-sized butter bits.

Add Buttermilk & Fold Layers: Pour in cold buttermilk and gently stir with a fork just until a shaggy dough forms. Turn out onto a lightly floured surface. Gently pat dough into a 1/2-inch rectangle, fold in half, and repeat folding 4 times to create dozens of flaky layers.

Cut & Bake Biscuits: Pat dough to 3/4-inch thickness. Using a 2.5-inch biscuit cutter pressed straight down without twisting, cut out biscuits and place them touching each other on the baking sheet. Bake for 14 to 16 minutes until tall, puffed, and deeply golden-brown. Brush tops immediately with melted butter.

Brown the Country Sausage: While biscuits bake, crumble the breakfast sausage into a large deep cast-iron skillet over medium-high heat. Cook for 6 to 8 minutes, breaking into crumbles with a wooden spoon, until browned and sizzling. Do not drain the rendered fat!

Roux & Whisk in Milk: Sprinkle 1/3 cup of flour directly over the sausage and rendered drippings in the skillet. Stir constantly for 1 to 2 minutes to cook out raw flour flavor. Gradually pour in the whole milk in a steady stream while whisking continuously to prevent lumps.

Simmer, Season & Smother: Reduce heat to medium-low. Simmer the gravy for 4 to 5 minutes, stirring frequently, until thick, creamy, and bubbling. Season generously with freshly cracked black pepper, salt, and garlic powder. Split warm biscuits in half, ladle thick sausage gravy lavishly over the flaky layers, and serve immediately!