Preheat oven to 425 and line a baking sheet with parchment paper.
Add flour, sugar, baking powder and salt to food processor and combine. Add cubes of butter to mixture and mix until the flour resembles a coarse crumb.
In separate bowl combine egg, yolk and 1/3 cup milk.
Add egg mixture to the food processor bowl and run until a ball forms. You can add more milk to soften the dough.
Turn out onto lightly floured surface and knead gently. Form into a ball.
Roll out to 1/2 inch thick circle and cut into wedges about 2 inches wide. Place 1 inch apart on prepared baking sheet.
In a small bowl beat egg white until frothy and then brush over the top of dough wedges and sprinkle lightly with sugar.
Bake for 12 to 14 minutes until the tops are golden brown. Cool on wire rack for 5 to 10 minutes before serving.