Combine peanut butter, butter and chocolate chips in a microwave safe bowl.
Microwave for 1 minute, then stir to blend ingredients thoroughly. Add vanilla. Stir well.
Place the Crispix cereal in a large bowl. Pour the peanut butter-chocolate mixture over the cereal. Toss to make sure all the cereal gets a good covering.
Coat with powdered sugar, sprinkling evenly over the cereal and tossing as you sprinkle to cover each piece well.