Directions

1. Sift flour and salt into a bowl and mix, then set aside.
   
2. Place butter into the bowl of a standing mixer with a paddle attachment. Turn the mixer on high speed and beat until fluffy, 5 minutes.
   
3. Gradually add sugar slowly, continuing to mix until pale and fluffy. Add flour all at once and mix until combined. Add vanilla then mix to incorporate.
   
4. Spray an 8x8 inch pan with cooking spray. Pat and roll shortbread into pan no more than 1/2-inch thick. Refrigerate for at least 30 minutes.
   
5. Preheat oven to 300 F. Take the shortbread out of the fridge and prick with fork across entire shortbread then cut into rectangles. Bake until golden and make sure the middle is firm, bake for 50-60 minutes.
   
6. Cool completely. Re-slice them, if necessary, and serve.