Preheat oven to 350 degrees and line an 8 inch square baking dish with parchment paper. Set aside.
In a medium mixing bowl, combine melted butter and sugar and stir until combined. Add egg and vanilla and stir until thoroughly incorporated. Add flour, baking powder and salt and stir until just combined. Gently stir in candy bars.
Pour batter into prepared pan and spread so evenly distributed. (Batter will be thick.) Bake for 25-30 minutes or until toothpick comes out clean.
Remove from oven and let cool completely. Remove from pan using the parchment paper, cut into squares and serve.