Preheat the oven to 200°c. Line a large baking tray with parchment paper.
In a large bowl, combine flour, baking powder, salt, garlic powder, and mustard powder. Lightly stir together with a fork.
Place the cold butter cubes in the bowl of dry ingredients. Toss to coat them in flour, then use your hands, or a pastry cutter, to break apart the butter pieces and blend them into the flour. Keep cutting the butter into the flour until the pieces are small and the mixture looks like sand. Work quickly to prevent the butter from melting.
Add the cheddar to the mixture and stir with a fork until evenly incorporated. Add the buttermilk. Mix with a rubber spatula, wooden spoon, or your hands.
Use a large ice cream scoop to scoop the dough into 12, onto the baking tray. Use your hands to help smooth the sides if necessary. Bake for 14-16 minutes.
While baking, mix the melted butter, parsley, garlic powder, and salt. Once removed from the oven, immediately brush the scones with the mixture. Let cool for at least 5 minutes before serving.