1. Preheat the oven to 300°F.
2. In the bowl of a stand mixer, place unsalted butter and powdered sugar, and cream it together until its soft and smooth.
3. In a large bowl, sift together, flour, cornstarch and salt.
4. Blend the butter mixture on slow, and add flour mixture in small batches.
5. Blend until all the flour mixture gets incorporated to make dough, and leave aside.
6. In a large pot, heat water, lemon juice, zest, cardamom and add dates. Allow to boil stirring continuously.
7. Reduce the heat to medium and allow to simmer for about 10 minutes or until the dates are soft.
8. Remove the pot from the stove and stir in vanilla extract, and mix well.
9. In a parchment lined baking tray, put the date mixture and spread it evenly.
10. Allow the date mixture to cool completely.
11. In another parchment lined baking tray, place 2/3 of prepared dough and flatten it to cover the bottom of pan.
12. Using hand, smoothen the surface of the dough evenly.
13. Bake in oven for 10 to 15 minutes, or until it get light brown color.
14. Remove the baked dough and allow to cool completely.
15. Layer the date mixture over the baked dough evenly.
16. Crumble the remaining dough and sprinkle over the dated mixture, and spread evenly.
17. Bake in the oven on top rack for 5 minutes, until the top is lightly golden in color.
18. Remove the baking tray and allow to cool.
19. Using a scrapper, loosen the edges.
20. Place a parchment paper on top, and turn over the baking tray over the parchment paper.
21. Carefully flip the pastry and remove from pan.
22. Place the chopping board over the pastry and flip it to get the crust down.
23. Using sharp knife, cut the pastry in 1 inch by 2 inch pieces.
24. Serve warm with tea or coffee or as desired.