1. Preheat oven to 350ºF (175ºC) degrees. Line two baking sheets with parchment paper.
2. In a food processor, blend the all-purpose flour, whole wheat flour, ground almonds, butter, sugar, vanilla and salt, and process until the mixture looks crumbly.
3. Add water and tahini and process until a smooth dough begins to form. Remove the dough from the food processor bowl and knead it a few times on the counter until smooth. (If the dough feels very dry, dampen your hands and knead the dough slightly.)
4. Create small balls of the dough, place them on the baking sheet, then flatten each one slightly with your fingers.
5. Bake for about 12-14 minutes, or until golden brown.
Cool completely and serve.