Preheat oven to 350° F.
Line a 9x13" baking pan with parchment paper.
In a medium bowl, mix together butter and sugar until combined well.
12 T unsalted butter, 1 1/2 cups light brown sugar
Add eggs and vanilla extract and stir in.
2 eggs, 1 T vanilla extract
Combine flour, salt, and baking powder, and sift into the butter mixture.
1 1/2 cups all purpose flour, 1/2 t salt, 1 t baking powder
Fold in and be careful not to overmix.
Fold in pecans, and pour into the pan.
1 cup pecan pieces
Drizzle/spoon the melted caramelized white chocolate on the top of the batter and swirl.
Bake for 22-25 minutes or until set and baked through.
Cool to room temperature and cut into squares.