Add Flour, Sugar, Butter, Cornstarch, and Salt into a large working bowl.
Rub by hand (wash your hands first) combining all the ingredients with your fingers until you have nice crumbs. Using your hands helps incorporate the butter as the warmth of your hands helps soften the butter.
Add the Vanilla Bean Paste
Continue to work the dough with your hands until well combined into a a large ball.
Lightly flour the shortbread mold, be sure to shake off excess.
Press the dough into the mold tightly.
You can also roll out the dough and cut it into the shapes of your choice, either by hand of with a cookie cutter.
Turn the mold upside down onto a parchment lined baking sheet.
Pierce the top all over with a fork.
350˚F for about 20 minutes. It will be a nice golden brown. Be careful not to over cook, i.e. no dark brown color.
Remove from oven and immediately score while still hot/warm from the oven. Don't score (cut) deeper than a third of the way down.
Dust the entire shortbread with granulated sugar.
Let cool for at least 1 hour.
Notes
The cornstarch softens the crumb of the shortbread so it melts in your mouth. I use powdered (confectioners) sugar as it combines well and adds to the softness of the shortbread.You can also add lemon zest, orange zest, chocolate chips, dried berries, etc.