1. Preheat oven to 325 degrees. Line a 9x13 pan with parchment paper for easy removal (see photos on website). Note: if you like a thinner bar, use a jelly roll size pan.
2. In mixer with paddle attachment, combine 4 sticks softened butter, sugar, powdered sugar and vanilla. Mix until well combined. Add flour and mix until completely combined. This mixture will be crumbly but moist.
3. Take half of the mixture and press it into the bottom of your prepared pan. Leave the other half in the bowl, to be used later. Bake for 20 minutes or until edges are slightly golden brown. Once out of the oven let cool for 15 minutes. While crust is cooling, make the caramel layer