Butter a half sheet baking pan and line with a parchment paper, with extra on long sides to help lift it out
In separate bowl add the Rice Krispies, Biscoff cookies, and remaining 4 cups of marshmallows and stir until evenly mixed.
Melt the butter in a large pot over medium heat. I like to brown my butter, meaning you allow the butter to cook until it begins to brown on the bottom.
Add the cookie butter and all but 4 cups of the marshmallows and stir until both are melted and smooth. Remove from heat.
Pour in the melted marshmallow and cookie butter into the Rice Krispie bowl, stiring and mixing as you pour it in.
Gently press into the prepared pan. Use the wrappers from the butter (or your hands buttered) to press down.
Refrigerate for 15-30 minutes to help them set up and cool down.
Make the cookie butter glaze by combining the 6 tablespoons of melted butter with the 1.5 cup of cookie butter and stirring until smooth, then spread it evenly over the cooled Rice Krispie treats with a spatula.
Take your 8 cookies that you crushed & sprinkle over the top of the glaze
Refrigerate for another 15 minutes to help the glaze set a bit.
Lift from baking pan and slice into 24 even squares & enjoy!