In a mixing bowl, combine the eggs, sugar, oil and pumpkin. Beat at medium speed until smooth. Next, mix your dry ingredients. Look how gorgeously yin-yangy my 1/2 and 1/2 whole wheat and white flour looks:
Add in the spices.
Start pouring dry ingredients into mixer, and mix well. Spread into a 15 x 9 x 1 jelly roll pan.
Bake at 350 degrees for 25-30 minutes, until a toothpick inserted in the middle comes out clean. Cool completely on a wire rack.
Melt white chocolate chips in a glass bowl in the microwave for 1 minute on medium-high heat (70%). Stir, and you'll magically see how they continue melting until smooth. If needed, heat another 10 seconds on 70% and stir. Gently fold melted white chocolate into whipped topping. Sprinkle in 1/2 tsp cinnamon for extra color and flavor.
Carefully break the cake into chunks. I ended up only needing about 3/4 of the cake, but a larger trifle bowl could hold the entire cake.
Layer Pumpkin Spice Cake chunks on the bottom of the bowl, then lightly spread a layer of white chocolate whipped topping. Repeat two more times, ending with topping on top.
Sprinkle a few cake crumbs on top, or if you have graham crackers or gingersnaps on hand, those crumbs would do nicely as well.