Line 2 baking sheets with parchment paper.

In a large bowl whisk the butter, brown sugar and vanilla till smooth. Add the egg and whisk again. Add the dry ingredients and fold in. Add the chopped dates and fold again.

Divide the dough into 8 equal portions, roll into balls and place on one of your baking sheets (the cookies can be close together at this point). Cover with plastic wrap and refrigerate for at least 1 hour and up to 2 days.

Divide the cookie balls between your 2 baking sheets, spacing them evenly apart. Place one of the baking sheets into the oven and bake till the edges are golden brown and the cookies are puffed up. Remove from the oven and flatten the cookies with a spatula. Return the pan to the oven, turn the oven off and leave for an additional 5 minutes. The cookies should be slightly puffed up and more golden brown all over.

Remove the pan from the oven and flatten the cookies again. Sprinkle with flaky sea salt. If you want a more finished look you can "scoot" the cookies using a bowl, glass or cutter that is slightly larger than the cookie. Let cool on the pan.

Return the oven to 375 degrees and repeat these steps with the second batch of cookie dough. Let the cookies cool completely before serving.