Dump Truck Cake

I've been looking forward to posting this idea for a while now.  Perusing the construction-themed cake options online and at Michael's, I was disappointed.  I brainstormed a bit, ran ideas by a coworker, and decided to make my own dump truck cake.  I figured it could be pretty straightforward- a sheet cake with a loaf cake on top to be the cab, graham cracker walls for the truck bed, and... something... as filling in the truck bed.  I used a chocolate cake recipe from Martha Stewart, and her vanilla frosting recipe as well.  Christopher decided that yellow frosting was in order.  As far as that truck filling, well, inspiration hit after I'd carved the top off the sheet cake and carved the loaf cake to have a sloped, cab-like look.  I had piles of cake bits sitting around when Eureka! Instant truck filling!  Mixed in with some Reese's peanut butter cups and graham crackers, I had insta-dirt.  YUM.  I cannot WAIT to dig into this treat at my son's birthday party tomorrow!

Detailed pictures after directions.

Supplies

Cake

• Butter, for coating cake pans
• 1 1/2 cups unsweetened cocoa powder, plus more for dusting
• 3 cups all-purpose flour
• 1 tablespoon baking soda
• 1 1/2 teaspoons baking powder
• 1 1/2 teaspoons salt
• 3 cups sugar
• 3/4 cups vegetable oil
• 1 1/2 cups buttermilk
• 1 1/2 teaspoons vanilla extract
• 3 large eggs, lightly beaten
• 1 1/2 cups hot water

Frosting

• 1 1/2 cups (3 sticks) unsalted butter, room temperature
• 1 lb (4 cups) confectioner's sugar, sifted
• 1/2 teaspoon pure vanilla extract
• Gel food coloring (I used yellow)

Decorations

• 4 graham crackers
• 4 Oreos
• Jelly beans (2 red, 2 white)
• 2 pretzel rods
• 12 Reese's peanut butter cup minis
• Chocolate cake pieces

Directions
Cake

1. Preheat oven to 350°.  For the dump truck cake, I used one 9 x 13 pan and one 9 x 5 pan (loaf size).  Butter cake pans.  Line bottoms with parchment paper, and butter paper.  Dust the pans with cocoa, and tap out the extra.
2. Sift cocoa, flour, baking soda, baking powder, salt, and sugar into a mixing bowl.  Fit the bowl into the base of your stand mixer, and one ingredient at a time mix in the oil, buttermilk, vanilla, eggs, and hot water, mixing at low speed.  Beat until smooth, about 2 minutes.  The batter will be very thin.
3.  Pour batter into pans.  I filled the loaf pan about 1/3 full, and the sheet pan about 1/2 full.  Bake 45 to 55 minutes, or until a toothpick inserted into the centers comes out clean.  My cakes were done at 45 minutes.
4. Let cakes cool in pans on wire racks, 20 minutes, before inverting to remove.  Discard paper.  Cool completely on racks, tops sides up.  Cut off top of each cake for a flat, smooth top.  Cut a slope into the loaf pan for the truck's windshield.  Set aside scraps for dump truck filling.  Place the small loaf cake on top of the large cake, then frost.

Frosting

1. In a stand mixer, beat butter on medium-high speed until pale and creamy, about 2 minutes.
2. Reduce speed to medium.  Add the powdered sugar, 1/2 cup at a time, beating well after each addition and scraping down the sides of the bowl as needed.  After every two additions, raise the speed to high and beat 10 seconds to aerate the frosting, then reduce to medium speed again.  Frosting will be very pale and fluffy.
3. Add vanilla, and beat until frosting is smooth.  Spoon about 1 cup of frosting into a pastry bag fitted with a round writing tip.  Add about 1/4 teaspoon gel food coloring and mix, adding more if needed, until frosting reaches desired color.  Scrape down sides of bowl to thoroughly incorporate food coloring and mix until color is even, without any white streaks.

Note: If not using immediately, frosting can be refrigerated up to 10 days in an airtight container.  Before using, bring to room temperature, then beat on low speed until smooth again (about 5 minutes).

Decorate

1. Thoroughly frost the cake, on all sides, with colored frosting.  Apply a thinner layer to start, and then cover with additional frosting for a smooth top coat.
2. Place graham crackers along 3 sides of back of cake.  For the edge along the bumper, just break one graham cracker in half, and pipe white frosting along the seam.  Place Oreos as wheels on cake.  Put two white jelly beans on front bumper as headlights, and two red jelly beans on back bumper as tail lights.  Gently insert pretzel rods in truck cab as exhaust pipes.  
3. Pipe on detail with the white frosting: windows, and windshield, truck grill, along graham cracker truck bed, license plates, and wheels.  For the windshield, I piped on the frosting generously and spread with a knife.
4. Fill dump truck bed first with leftover cake scraps from trimming the cakes, broken into pieces.  Chop Reese's minis and sprinkle over cake pieces.  Crush remaining graham cracker half and sprinkle over top.  Add more as desired.  A couple gummy worms could be welcome additions, too!

Carved, stacked cakes

Alternate side of the cake

Back.  Those jelly bean tail lights are too cute.

"Dirt" filling