Preheat the oven to 350 degrees. Line the baking dish with parchment. Set aside.
Melt the butter in a small saucepan until browned and it begins to have a nutty aroma.
Transfer the browned butter to a large bowl.
Whisk in HALF of the biscoff spread, working until it completely melts into the butter.
Stir in the brown sugar and granulated sugar until combined.
Add the eggs and vanilla - mixing until the mixture until smooth and shiny.
Fold in the flour and salt - working the batter until it is combined and thick.
Fold in both varieties of the chocolate chips as well as HALF of the crushed cookies.
Transfer the batter to the prepared baking pan, spreading it into an even layer.
Top with the remaining chocolate chips, butterscotch chips, and crushed cookies.
Bake for 25-20 minutes or until the toothpick test comes out clean.
Cool for 30 minutes before removing from the pan and cutting.
Before serving, melt the remaining biscoff spread in the microwave and then drizzle it over the tops of the brownies.