Chop candy bars into small chunks, place on a baking sheet (or something similar) and freeze for 30mins.
Preheat oven to 350°F. Spray and 8" x 8" pan and line with parchment.
In a small bowl, whisk together flour and baking soda, set aside.
Beat butter and sugars on medium until light and fluffy (approx. 2-3mins).
Reduce speed and add sea salt, egg, and vanilla. Beat until well combined.
Add flour mixture a little at a time and mix until just combined (do not overbeat).
Fold in the frozen cookie chunks and spread the mixture evenly in your prepared pan. I found an offset spatula worked best for this.
Top with additional candy bar chunks if desired.
Bake for approximately 25mins or until golden on the edges, but still somewhat gooey in the center. A cake tester should come out mostly clean, but not completely clean. Start checking at 20mins.
Remove from oven. Cool completely on a wire rack.
Cut, serve, devour.
Notes
*I used 1/2 a KitKat, 1/2 a Coffee Crisp, 2 Peanut Butter Cups, and 1/2 a box of smarties. Plus a bit more for topping.