Start by grating the frozen butter on the coarse side of a cheese grater. This will help incorporate the butter quickly and easily.
In a large bowl, mix together the flour, sugar, baking powder, baking soda, garlic powder, black pepper and salt. Add the grated butter and using your fingertips, swiftly rub the flour and butter together to form a fine, breadcrumb-like texture.
Add the chili, cilantro, green onions and cheese. Mix together.
Next, pour in the buttermilk. Use a spoon to bring the mixture together as a soft dough. Be very gentle and do not knead it. Light and flaky scones require as little handling as possible.
Flour your hands and work surface. Transfer the dough onto the floured surface and pat or roll the dough out to a thickness of about ¾ inches. Fold one side into the center, then the other side. Now, turn the dough horizontally and again gently flatten into a ¾ inch thick rectangle. Repeat this process 2 more times (total of 3 times), so you end up with a ¾ inch thick rectangle. Stamp out rounds using a cookie cutter/glass with thin edges. Pick up any scraps of dough and bring them back together to cut out more rounds. Remember to handle the dough quickly and with a light touch. Cracks on the surface are fine. Scones should be rustic looking.
Place the scones on a large baking tray lined with baking parchment. Arrange the scones on the tray, leaving a small gap around each one as they will rise a bit. Refrigerate for 15 minutes.