Start by preheating your oven to 400°F and lining a baking tray with parchment paper. In a large bowl, whisk together flour, baking powder, baking soda, salt, and black pepper. Mixing the dry ingredients first helps distribute the leavening evenly.
Add the cold cubed butter into the flour mixture. Use a pastry cutter or fork to work the butter into the flour until it resembles coarse crumbs. Small butter pieces create flaky layers once baked.
Stir in the freshly grated Irish cheddar cheese and chopped chives. Tossing them with the flour prevents clumping and helps distribute flavor throughout the dough evenly.
In a separate bowl, whisk together the buttermilk and egg until smooth. Pour the mixture into the dry ingredients and gently stir until the dough just comes together. Avoid overmixing because it can make the scones dense.
Transfer the dough onto a lightly floured surface and gently knead it a few times. Pat the dough into a round disk about one inch thick. Keeping the dough thick helps create taller, softer scones.
Use a sharp knife or bench scraper to cut the dough into 8 wedges. Place the wedges slightly apart on the prepared baking sheet so they bake evenly and develop crisp edges.
Brush the tops with heavy cream for a golden finish. Bake for 18–22 minutes or until the tops are golden brown and the centers are fully cooked. The cheese will become bubbly and slightly crisp around the edges.
Allow the scones to cool for about 5 minutes before serving. They taste best warm when the cheese is still soft and flavorful.