In a microwave safe bowl, combine 2 1/2 c white chocolate chips and the chocolate chips.
Microwave on high for 2 minutes, stir.
Microwave for another 1 to 2 minutes and stir until smooth.
Immediately add marshmallows, cereal, and walnuts. Mix well.
Spread evenly into a 13 inch pizza pan coated with nonstick spray.
Arrange cherry halves and sprinkle with coconut flakes.
Microwave remaining white chocolate chips on high for one minutes.
Add oil and stir until smooth. Drizzle over pizza.
Chill until firm. Serve at room temperature.