Preheat oven to 400 degrese F and line a large baking sheet with parchment paper.
Mix the flour, sugar, salt, baking powder, and baking soda in a large bowl.
Add the cubed butter and cut it into the dry ingredients with a fork or pastry cutter.
In another small bowl, mix together the buttermilk, egg, and vanilla.
Slowly add the wet ingredients to the flour mixture and mix until just combined. Avoid overmixing.
Divide dough in two and roll out on a floured surface. Fold dough in half and then in quarters. Roll out again and repeat the folding process to laminate.
Shape dough into two 6 inch discs and cut each disc into 6 pieces and arrange on the prepared baking sheet.
Brush with the egg white and sprinkle with the turbinado sugar.
Bake for 15-17 minutes or until they begin to turn golden brown.
