Place white baking chips and whipping cream in small microwavable bowl. Microwave uncovered on Medium-High (70%) 1 minute; stir. Microwave 10 to 15 seconds longer or until mixture can be stirred smooth. Spread over baked layer. Sprinkle with nuts; press gently into topping. Cool completely, about 1 hour. For bars, cut into 8 rows by 4 rows.