Heat oven to 350 degrees
Cream together butter, granulated sugar, and 1/2 cup of the brown sugar
Add 2 egg yolks and combine fully
Mix in vanilla and water
Combine flour, baking powder, baking soda, and salt in separate bowl
Slowly blend dry mixture into wet ingredients
Spread batter into prepared 9X13 pan
Sprinkle with butterscotch chips and cashew pieces (batter should be mostly covered)
Beat egg whites until soft peaks form
Add the remaining one cup of brown sugar in 3 batches (1/3 cup measurements)
Combine each fully and then whip whole mixture to firm/stiff peaks
Spread egg whites over the top of bars
Bake for 20-25 minutes, until edges of bars and top of meringue brown a bit