Add the cereal to a large mixing bowl and set aside.
Add the chocolate chips, cookie butter, and butter to a medium-sized microwaveable bowl (or melt using a double broiler).
Microwave for about a minute. Stir the mixture, then microwave in 15 second intervals (stirring after each) until melted and creamy.
Stir in the vanilla.
Pour the chocolate mixture over the cereal. Mix until the pieces are well coated.
Open up a large resealable plastic bag. Pour in 1 cup (125 g) of powdered sugar, then about half of your cereal mixture. On top, add another 1/2 cup (62 g) of powdered sugar and zip the bag tightly.
Start shaking the bag (we recommend doing this over a sink or garbage can in case of any spills or loose powdered sugar!) and shake until the pieces are evenly coated. Add more powdered sugar, if needed. Pour into a clean bowl/container. Add some crushed Biscoff cookies, if using.
Repeat steps 6 through 8 with the second half of your cereal (you can use the same bag if the seal still works).
Serve and enjoy! If desired, top with some crushed Biscoff cookies. This stays fresh in a tightly sealed container for 2-3 days.