Preheat oven to 350° F. Spray an8x8 baking pan with cooking spray and line the bottom with parchment paper for easy release.
In a large mixing bowl, mix together in melted butter and brown sugar until well combined.
Add in eggs and vanilla extract and continue to mix until well combined.
Add flour, cornstarch, baking powder, baking soda, and salt. Mix until the wet ingredients and dry ingredients are combined. Do not overmix the batter.
Add your desired mix ins into the batter. Gently fold in the coconut, chocolate chips, and caramel bits until they are dispersed throughout the batter.
Pour the batter into your prepared baking pan and spread to create an even layer.
Bake the blondies approximately 40 minutes or until a toothpick comes out clean. The blondies will be a light golden brown color.
Cool to room temperature in the pan. Remove the blondies from the pan and cut into squares.