Place flour, sugar, salt, and butter into the mixing bowl. Place on low and mix until dough forms a cornmeal type texture.
Add yolks and vanilla. Mix until dough forms.
Take the parchment paper and cut it to fit the pan you are using. Simply cutting the parchment to fit the bottom of the pan will be all you need.
Spray the pan, place the parchment paper into the pan, and spray the parchment and the sides of the pan.
Place dough in the center of the pan and form it to the edges of your pan making it as even as possible.
Place in oven for 15-20 minutes and cook until a light golden brown.
Remove from oven and let the tart cool to room temperature.
If you used a tart pan, you can remove the shortbread from the pan. If you used the rectangular pan, leave the shortbread in the pan.
for the salted caramel
Place cream into one of the sauce pans and bring it to a simmer. Once it simmers, turn down to low to keep warm.
Place sugar and water into the other sauce pan and mix.
Cook the sugar and water on medium high without stirring until water evaporates and sugar begins to caramelize. Remove from heat when you have a light golden brown color.
Remove cream from heat and whisk into the caramelized sugar. The mixture will bubble rapidly and steam. This is normal due to the remaining mositure and difference in temperatures. Continue whisking to incorporate all of the cream.
Set aside to cool down. Once the caramel comes to room temperature, you can pour it onto the tart or directly into your rectangular pan. Place in the refrigerator for 2 hours (or overnight) to set.
Once caramel has set, cut into desired shapes or numbers. Sprinkle with finishing salt and serve.
Notes
you can do ¼ cup regular and ¼ cup brown sugar for a more chewy shortbread.
You can omit this step and simply add finishing salt to the top of the caramel upon serving.
You can also use a 9 x 9 baking dish instead of the tart pan.