YIELD: ½ sheet pan
TOTAL TIME: 90 min + overnight
Preheat an oven to 325 degrees F. Line a baking sheet with parchment paper and lightly grease.
Cream butter, sugar and vanilla in an electric mixer with paddle attachment. Add flour and salt, mix to combine./p>
Pour out onto baking sheet and press down evenly. Bake until golden brown 35-50 minutes.
Melt lemon juice, sugar and butter in a medium saucepan over medium heat. In a separate bowl, add yolks. Temper the yolks by adding a small amount of the hot liquid to the yolks while whisking. Continue to slowly add hot liquid while whisking. Return yolks and liquid to saucepan and whisk to thicken. Bloom gelatin according to the box and add to the warm liquid whisking.
Pour the filling over the baked cookie bar crust, and chill to set.