Preheat your oven to 350°F.

Spray three 9-inch round cake pans with baking spray.

In a large mixing bowl, combine the cake mix, egg whites, water, and canola oil.

Using a hand mixer, beat until the batter is smooth and well combined.

Divide the batter evenly among the three prepared cake pans.

Bake for 28–32 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cakes to cool completely before assembling.

Make the Buttercream Frosting

In the bowl of a stand mixer, combine the softened butter, powdered sugar, heavy whipping cream, and vanilla extract.

Beat until the frosting is smooth, fluffy, and forms stiff peaks.

Transfer about 1 cup of frosting into a piping bag fitted with a large star tip.

Prepare the Twinkies

Cut approximately 3 Twinkies into bite-sized chunks for the cake filling.

Slice 3 to 4 additional Twinkies in half for decorating the top of the cake.

Assemble the Cake

Place the first cake layer onto a 10-inch cake board.

Trim the rounded top (the dome) off the cake to create a flat surface.

Repeat with the remaining two cake layers.

Spread about 1 cup of buttercream frosting evenly over the first cake layer.

Sprinkle half of the chopped Twinkie pieces over the frosting and gently press them into place.

Add the second cake layer.

Spread another 1 cup of frosting evenly across the top.

Sprinkle the remaining chopped Twinkies over the frosting.

Place the final cake layer on top.

Frost the top and sides of the cake with the remaining buttercream until smooth.

Add the Vanilla Drip

Remove the seal from the container of vanilla frosting.

Microwave the frosting for 30–45 seconds, just until it becomes pourable but not overly thin.

Pour some of the melted frosting into a squeeze bottle.

Carefully squeeze frosting around the top edge of the cake, allowing it to drip naturally down the sides.

Decorate the Cake

Pipe decorative dollops of buttercream around the top edge of the cake using the prepared piping bag.

Place one halved Twinkie between each frosting dollop.

Refrigerate the cake for about 30 minutes before slicing for cleaner, more even pieces.