In a large mixing bowl, combine the white whole wheat flour, all-purpose flour, granulated sugar, cinnamon, and kosher salt. Whisk the dry ingredients together until evenly blended.
Add the cold, cubed butter to the dry ingredients. Using a pastry cutter or your fingers, mix until the mixture resembles coarse crumbs.
In a separate bowl, mix together the cold water and vanilla extract. Gradually add this to the flour mixture, stirring gently until the dough comes together.
Divide the dough into two portions for easier handling. On a lightly floured surface, roll out one portion to about 1/8 inch thick.
Using a sharp knife or a pizza cutter, cut the rolled-out dough into small squares, about 1 inch in size.
Preheat your oven to 350°F (175°C). Line your baking sheets with parchment paper and spread the squares out evenly. Bake for 15-20 minutes, or until they are golden brown and crisp.
Once baked, remove the squares from the oven and let them cool. Brush them lightly with melted butter and sprinkle with additional cinnamon and sugar if desired.
