In large microwavable bowl, mix cereals and walnuts.
In 2-cup microwavable measuring cup, microwave butter on High 30 seconds or until melted. Stir in brown sugar, cinnamon, ginger and nutmeg uncovered for about 1 minute, until smooth and bubbly. Pour over cereal mixture; stir until evenly coated.
Microwave uncovered on High 4 minutes, stirring after each minute. Spread on waxed paper or foil to cool. Sprinkle apples evenly over cereal mixture.
In small microwavable bowl, microwave white vanilla baking chips and shortening uncovered on High about 1 minute or until chips can be stirred smooth. Drizzle over cereal mixture; let stand until set. Break into bite-size pieces. Store in airtight container.