Preheat Oven to 325 F (163 C) and line a 9 x 13 inch glass pan with overhanging parchment paper.
In medium bowl hand whisk together flour, sugar, salt, and ginger.
Add vanilla extract and softened butter to flour mixture.
Gently mix together with hands until massaging until a soft shortbread dough is formed.
Transfer dough to baking pan and gently press across bottom of pan into an even layer. Wet fingertips or rubber spatula with cold water to help preventing sticking as you level dough.
Place pan on middle rack of oven and bake for 18-20 minutes until slightly golden.
While shortbread is baking mix together filling.
In a large bowl hand whisk together all ingredients until smooth liquid.
Remove pre-baked crust from oven and pour filling directly onto hot crust.
Place pan back in the oven and bake for an additional 22-24 minutes until center is set without any wobbling.
Remove pan from oven again and place on a cooling rack until completetly cooled.
Cover cooled pan with plastic wrap and place in fridge to set and chill for 1.5-2 hrs.
Run an offset metal spatula around the edges of pan to loosen bars. Lift parchment paper from pan by pulling up on overhanging sides. Set on a cutting surface.
Using a sharp knife slice into squares. Dust lightly with powdered sugar and serve.