Tender semi-homemade vanilla cake layers filled with creamy vanilla buttercream decorating to look like your favorite winter sweater.
Preheat oven to 350 °F. Spray three 6-inch round cake pans with non-stick spray, line the bottom of each pan with parchment paper and spray again. Set aside.
In a medium-size bowl, whisk and stir together the cake mix, all-purpose flour, and salt. Set aside.
In the stand mixer bowl fitted with a paddle attachment, beat the butter, oil, and sugar on medium-high for 5 minutes.
Add eggs, one at a time to the stand mixer bowl and beat on medium until well incorporated.
Turn the mixer on low and add half of the flour mixture to the butter mixture until fully incorporated.
Add the vanilla and milk and beat on low until incorporated. Scrape down the sides of the bowl. Finish by adding the remaining flour mixture and mix on medium for another 30 seconds.
Evenly distribute the cake batter among the three cake pans and bake for about 30-35 minutes or until a toothpick inserted into the center of each cake comes out clean or with just a few moist crumbs.
Remove cakes from the oven and let cool in pans for 10 minutes before inverting onto cooling racks to cool completely. Wrap cakes in plastic wrap and place into the freezer to chill for 30 minutes.
In the stand mixer bowl fitted with the paddle attachment, beat the butter until light and fluffy, about 2 minutes.
Turn the mixer to low and gradually add the powdered sugar, followed by the cream, salt, and vanilla extract. Mix until combined. Mix until incorporated completely. Scrape down sides of the bowl.
Add 1-2 drops of ivory gel food coloring to dye the buttercream a light ivory color.
Turn the mixer to medium-high and beat the frosting for about 5 minutes until light and fluffy. Turn the mixer on low and mix for 2 minutes to push out any air bubbles.
Prepare 2 piping bags with couplers and ½ cup to ⅔ cups of ivory buttercream. You'll need the one of each piping tip - Ateco #32(french star tip), #17 (closed star tip), #11 (round tip), #6 (small round tip), and #233 (grass tip).
Remove the cake layers from the freezer and unwrap the cake layers. Next, use a serrated knife to cut off the dome of the cakes to make the layers flat and even.
Add a small amount of buttercream onto the center of the cake board. Layer one vanilla cake, cut side up onto cake board. Add a 2/3 cup of vanilla buttercream over the cake.
Place another cake layer cut side down over the top. Repeat the process for another layer — Crumb coat with ivory vanilla buttercream and freeze for 30 minutes.
Add a thin layer of ivory buttercream all over the cake. Use an offset spatula to fill in any gaps with more buttercream. Then use a cake scraper to smooth out the sides of the cake. Use the offset spatula to make the top edges sharp and smooth. Freeze for 15 minutes.
Next, with the cake scraper, mark 1 large column followed by 3 small columns all around the cake.
With the #32 piping tip, pipe a diagonal shell on the left of the center on the large column. Then pipe another diagonal shell on the right of center, slightly overlapping the previous shell, so you create a heart pattern. Repeat this step and continue to pipe shell hearts on all the large columns.
Next, with the #6 piping tip, pipe straight lines on the column mark you previously made going from the top to the bottom of the cake.
Then with the #17 piping tip, start from the top of the cake and the small middle column, pipe a twisted rope. Move your wrist counter-clockwise while squeezing the piping bag down the cake. Repeat this step and continue to pipe on the remaining middle columns.
With the #11 piping tip, pipe 8 dots per column on the remaining small columns.
On the top of the cake, pipe two rows of twisted rope borders with the #17 piping tip.
To create the sweater puff balls, insert a toothpick into each marshmallow, with the #233 grass tip pipe all over the marshmallow. Start by pressing the piping bag on the marshmallow and while squeezing pull the bag away from the marshmallow creating a grass-like effect. Repeat this process all over the marshmallows. Then insert each marshmallow into the side of the cake.
Finally, use the #11 tip, pipe two sweater drawstrings connecting to the marshmallow puff balls, then pipe a bow with buttercream on top of the cake. Serve cake at room temperature!