Preheat the oven to 350°F and line a 8x8 inch pan with parchment paper.
In a large bowl, mix together the browned butter, brown sugar, vanilla, and salt until combined. Then fold in the flour and mix until the dough comes together.
Press the dough into your lined baking pan and smooth into an even layer. Poke a few holes in the dough with a fork to allow air to escape while baking.
Bake the crust at 350°F for 15-20 minutes or until the top is lightly browned.
Remove from the oven and let cool while you make the filling (the crust does not have to cool completely before filling).
Pecan Pie Filling
Combine the butter, brown sugar, bourbon, vanilla, and heavy cream in a large saucepan over medium heat. Whisk to combine the ingredients and dissolve the sugar.
Bring to a boil and allow to boil for 3 minutes while stirring frequently. Carefully spoon about ¼ cup of the mixture into a glass measuring cup to temper the egg.
Whisk the egg in a small heat-safe bowl and slowly drizzle the ¼ cup of syrup into the egg as you continue to whisk (whisk continuously so that the egg doesn't scramble). Once the egg and ¼ cup of syrup are fully combined and smooth, then pour back into the syrup mixture and stir until combined.
Remove from the heat and stir in the Medjool dates, pecans, and cinnamon.
Pour the filling evenly over the slightly cooled cookie crust.
Bake at 350°F for 20-25 minutes or until a toothpick inserted in the center comes out mostly clean. If the top begins to get too brown, loosely cover with foil for the remainder of the baking time.
Remove from the oven and allow the bars to cool all the way to room temperature in the baking pan.
Once cool, use the parchment paper sling to pull the pecan cookies out of the pan and then slice into bars.
Store in an airtight container at room temperature for up to 5 days.To make brown butter: In a small saucepan, melt butter over medium heat. Once melted, stir frequently and watch closely for the formation of brown specs on the bottom of the pan and a nutty aroma. Once you see brown specs, stir for just a few more seconds (it browns super quickly). Remove from the heat and immediately pour into a different bowl to prevent it from burning. Let cool for 5-10 minutes.