Combine the chocolate chips, peanut butter, and vegan margarine in a microwave-safe bowl and heat for about 1 minute, or until melted. Add vanilla.
Place the cereal squares in a large container and pour in the chocolate mixture. Stir gently until all the squares are coated.
Add the powdered sugar to the container and seal with a lid. Shake gently until the sugar has coated all the squares.
Place in the freezer for 30 minutes, or until the chocolate hardens. Once solidified, store in the refrigerator.