In small microwavable bowl, microwave reserved white chocolate bar chunks and oil uncovered on High 30 to 60 seconds, stirring every 15 seconds, until melted; stir well. Drizzle glaze over bars. Or if desired, place glaze in small food-storage plastic bag and cut off small tip from one corner of bag; drizzle glaze in diagonal lines over bars. Let stand until glaze is set, about 3 hours. For bars, cut into 6 rows by 6 rows.