Preheat oven to 350°F.
Prepare 2 Cake Pans (8"x8"x2"): use bottom of cake pan to measure/trace 2 circles on parchment paper; cut out the circles and set aside. Spray the inside of the pans with canola oil. Place parchment circles in the bottom of each pan and spray over top with butter flavored oil. Set aside.
Prepare Cakes: in a large mixing bowl, whisk together eggs, oil, and water. Add both boxes of dry mix to the liquids in the bowl; stir with a large spoon, until the ingredients are just combined. Divide batter between the 2 cake pans and bake for 40 minutes or until a toothpick inserted in the center comes out clean. Remove cakes and let cool completely, about 1 hour.
Prepare Frosting: while cakes are cooling, prepare the frosting. Whip cookie butter cream cheese, cookie butter, and vanilla until fluffy, blended together, and thoroughly mixed. Refrigerate frosting until ready to use.
Prepare Milk Soak, Bananas, & Cake Layers: once cake is cooled, prepare the milk soak. Place 1 cup cookie butter and ½ cup milk into a sauce pan over a low flame; stir until melted together. Add a little more milk if needed to make it slightly runny.
Cut bananas into ¼ inch round slices.
Remove cakes from pans to a wire rack. Use a serrated knife to cut off cake crowns and slice each cake into 2 layers. Set the crowns aside for another use (ideas: crumbled & toasted for ice cream topping; use to craft trifles, banana bread pudding, or cake pops; blend into a chocolate shake).
Assemble Cake: place a dollop of cookie butter frosting on cake plate or platter to anchor. Place first layer of cake over the frosting and center on the plate. Spoon 1/3 of the cookie butter/milk soak over top of layer; frost; cover with sliced bananas. Repeat with second and third layers of cake. Add the fourth (top) layer and frost liberally. Decorate the top layer: place 8 (or so) cookie halves upright around the edge of the cake; place ¾ of walnuts and remainder of bananas around the center of the cake. Crush remaining cookies and walnuts and sprinkle over the cake. If you’re feeling bananas, drizzle with melted chocolate.