Preheat oven to 350°. Line a 9 x 13 inch baking pan with foil with the foil extending over the ends. This makes lifting out the brownies easier when finished. Spray foil with cooking spray and set aside.
Using a large bowl, beat butter, brown sugar and sugar with electric mixer on medium speed until light and fluffy.
Add eggs and vanilla, beat until combined.
In a small mixing bowl, whisk flour, baking powder and salt together. Add to sugar mixture and stir until combined.
Spread into prepared baking pan and bake for 25 - 28 minutes until blondies are set.
While blondies are baking, in a 2 quart saucepan melt butter then add brown sugar. Stir until dissolved.
Next, add corn syrup and continue to stir.
Slowly add condensed milk, stirring constantly.
Cook over medium heat stirring constantly. Once caramel starts to boil, continue cooking until caramel reaches 230°
When the caramel reaches 230° remove from heat, add vanilla, stir, then add cashews. Stir.
Once blondies have been removed from oven, spread caramel mixture evenly over the top.
In a microwave safe bowl, add chocolate wafers and cook for 30 seconds. Remove, stir, place back in microwave and cook for an additional 15 seconds. Stir and continue at 15 seconds intervals until chocolate has completely melted.
Lastly, spread chocolate over the top.
Let blondies cool completely before cutting.
Blondie recipe adapted from Betty Crocker