1. Pour the chex mix into a large bowl and set aside. 2. In a microwave safe bowl, combine the semi-sweet chocolate chips, butter, and biscoff. Microwave for 1 minute, stopping to stir. Microwave in additional 15 second increments if needed until the mixture is smooth. 3. Pour the chocolate mixture slowly over the chex mix, stirring to coat evenly. 4. Spread the chex mix mixture onto a cookie sheet and refrigerate for an hour or freeze for 10 minutes or until the chocolate is hardened. 5. Meanwhile, pour the powdered sugar into a ziploc bag. Once the chex mix is hardened break it up then put it into the ziploc bag and shake to coat well.