Stuffed Cake with 5 Flavors

For the sheet cake, unmold the cake from the pan and set it on a work surface in front of you with the narrow ends facing left and right. Score the cake vertically with a knife to create 5 even columns. Using the back side of a piping tip, cut 4 evenly spaced circles of cake from each column, being careful to only go about three-fourths of the way down; do not cut all the way through the cake. Pull out the resulting cake coins with your fingers and reserve them for later. If needed, use a skewer or offset spatula to dig each "hole" a little deeper to accommodate about 2 teaspoons of filling and about 1 teaspoon of topping. You should end up with a total of 20 holes, spaced as evenly as possible.   

For the fillings and toppings, each column will have a different flavor. (Note: Be sure not to overfill the holes. Also, you will have leftovers of all the fillings and toppings after this next step. Hold onto them for garnishing the cake after it's frosted.) 

Working from the left side of the cake to the right, start with the strawberry shortcake flavor. Spoon or pipe strawberry preserves into the first column of 4 holes and top each with graham cracker crumbs.  

For the banana pudding flavor, spoon or pipe vanilla pudding into the next column of 4 holes and top each with mashed or chopped bananas and crushed vanilla wafers. 

For the caramel pretzel flavor, spoon or pipe caramel sauce into the next column of 4 holes and top each with crushed pretzels. 

For the Funfetti flavor, spoon or pipe whipped cream into the next column of 4 holes and top each with sprinkles. 

For the cookies & cream flavor, spoon or pipe whipped cream into the last column of 4 holes and top each with crushed Oreos. 

Cover each hole with the reserved cake coins so that the pieces are flush with the top of the cake. Ice the cake with the buttercream frosting. Score the frosting vertically with an offset spatula or knife to mark the 5 columns again.  

To decorate the cake, place the 1 ½ cups whipped cream in a piping bag fitted with a star tip. Working from the left side of the cake to the right, start with the strawberry shortcake flavor. Dot the remaining strawberry preserves along the column and use a skewer to swirl them in a decorative pattern. Sprinkle the remaining graham cracker crumbs over the section, then pipe whipped cream over each filled hole and top with a strawberry. 

For the banana pudding flavor, sprinkle the column with the remaining crushed vanilla wafers. Pipe whipped cream over each filled hole and top with a vanilla wafer half and a banana slice. 

For the caramel pretzel flavor, drizzle the column with the remaining caramel and sprinkle with the remaining crushed pretzels. Pipe whipped cream over each filled hole and top with a mini pretzel. 

For the Funfetti flavor, pipe whipped cream over each filled hole in that column and top with the remaining rainbow sprinkles. 

For the cookies & cream flavor, sprinkle the column with the remaining crushed Oreos. Pipe whipped cream over each filled hole and top with an Oreo half. 

To serve, cut each column into 4 pieces, each with its own filling and topping.