Step 1: Preheat your oven to 425°F (220°C) and line a baking sheet with parchment paper.
Step 2: In a large bowl, whisk together the all-purpose flour, baking powder, granulated sugar, and salt.
Step 3: Add the cold, cubed unsalted butter to the dry ingredients. Using a pastry blender, two knives, or your fingertips, cut the butter into the flour mixture until it resembles coarse crumbs with some pea-sized pieces of butter remaining.
Step 4: Stir in the shredded sharp cheddar cheese and finely chopped fresh chives. Distribute them evenly throughout the flour and butter mixture.
Step 5: Make a well in the center of the mixture and pour in the cold buttermilk. Mix with a fork or a wooden spoon until just combined. Be careful not to overmix; the dough will be shaggy and slightly sticky.
Step 6: Turn the dough out onto a lightly floured surface. Gently knead it 5-6 times, just enough to bring it together. Do not overwork the dough.
Step 7: Pat or roll the dough to about 3/4 to 1 inch thickness. Use a 2-inch round biscuit cutter to cut out biscuits. Press straight down without twisting to ensure a good rise. Gather the scraps, gently pat them together, and cut out any remaining biscuits.
Step 8: Place the cut biscuits on the prepared baking sheet, leaving about 1 inch between them. If desired, brush the tops with a little extra buttermilk for a golden finish.
Step 9: Bake for 15-18 minutes, or until the biscuits are golden brown on top and bottom.
Step 10: Remove from the oven and let cool slightly on the baking sheet before transferring to a wire rack. These biscuits are best enjoyed warm.