A tribute to Pop's Chock'lit Shoppe, this dessert is a milkshake in cake form featuring malt Neapolitan cake layers and coated in a rich malt buttercream. It's as vibrant and dark as the town of Riverdale.
Preheat oven to 350 degrees F. Line 3 9 inch square baking pans with parchment paper and spray with nonstick spray.
Prepare boxed cakes according to package instructions, adding in 2 tablespoons of malt powder to each batter. Also add 1 teaspoon of strawberry extract to the strawberry batter.
Pour batters into prepared cake pans and bake for about 35-40 minutes or until a toothpick inserted in the center of the cake comes out clean.
Let cakes cool completely then trim tops to level. Chill cake layers while you make the buttercream and decorations.
Beat butter alone in a stand mixer fitted with a paddle attachment until fluffy. Add malt powder, salt, and about ½ cup of sugar. Beat until combined. Gradually beat in remaining sugar. Add the milk, vanilla, and food coloring. Beat to combine. Transfer frosting to a piping bag.
Pipe the outline of an arrow with red candy melts onto a parchment-lined baking sheet and let set. Fill the arrow with black candy melts and let set. Pipe a rectangle with white candy melts and let set. Flip white rectangle over and attach the arrow onto the smooth side of the rectangle with candy melts. Let set. Flip over and attach a skewer or lollipop stick to the back of the rectangle with candy melts. Let set.
Pipe a large half-moon with yellow candy melts onto a parchment-lined baking sheet, about 7 x 5 inches . Lay 4 large wooden popsicle sticks on top. Pipe yellow candy melts over the popsicle sticks and spread to cover with a small offset. Let set. Flip over and pipe black candy melts on the flat side to resemble leaves. Let set.
Pipe three rectangle outlines with red candy melts, about 3 x1 ½ inches, onto a parchment-lined baking sheet. Fill the inside of the outlines with orange candy melts and immediately cover with orange sanding sugar. Pipe a black hood with black candy melts and let set. Attach to one of the rectangles with candy melts.
Dust cornstarch over a work surface and roll out some red fondant. Use metal letter cutters to cut out 'D,' 'I,' and 'E.' Transfer to a parchment-lined baking sheet. Roll out some white fondant and cut out 'N' and 'R.' Set aside.
Position the chocolate cake layer on a cake board and top with a layer of buttercream. Top with the strawberry cake layer, another layer of frosting, and then the vanilla cake layer on top. Frost a thin layer of buttercream all over and freeze for 15 minutes. Frost entire cake with buttercream.
Position fondant 'DINER' letters on side of the cake in the center top area. Use a skewer to add indentations on the front and sides of a cake to resemble side paneling.
Stick on windows and door onto front of cake underneath 'DINER.'.
Pipe red drips on the sides of the cake with red candy melts. Cover top with red candy melts and spread with offset spatula. Immediately insert moon and arrow sign into top of cake.