Preheat oven to 400 F. Line a baking sheet with a silpat or parchment paper and set aside.

Combine dry ingredients {first 5} in a mixing bowl. Carefully grate frozen butter into flour mixture using the large holes of a box grater. Toss the mixture thoroughly to combine until it resembles a coarse meal.

In a separate bowl, whisk sour cream and egg together until smooth. Combine wet and dry ingredients and gently mix until large dough clumps form. Work the dough with your hands until a ball forms {be patient here because you might think the mixture is too dry to form a ball, but trust me it does come together}.

Press ball onto a floured surface, pushing down until a circle about 8 inches is formed {the dough should be about 3/4 inch thick}. Sprinkle with sugar and then cut into 8 triangles. Place the triangles onto the prepared baking sheet about 1 inch apart. Bake about 15 minutes or until golden.