Cream butter, sugar and Walnut vinegar in mixer. Add egg white, mix. Add flour, baking powder and cinnamon just till comes together.
Roll out onto baking sheet, press evenly (will cover about ½ the pan)
Whisk egg yolk with 2tsp water to egg wash top, sprinkle with nuts and cinnamon.
Bake at 350 degrees until light brown 15-20 min
