If your son or daughter is a huge fan of monster trucks, a 3-D monster truck cake is a wonderful birthday surprise. Luckily, since the trucks are pretty boxy, they are simple to replicate in cake form. It can be hard to visualize what a monster truck looks like, so keep a picture handy for reference.
Bake two 9-by-13 inch sheet cakes using a boxed cake mix or your own recipe. Take the cakes out of their pans and lay them on racks to cool for 20 minutes. Place one of the cakes on your serving board and frost the top and the sides with chocolate icing, or another icing that is a shade of brown. (This cake will be the ground.) Sprinkle graham cracker crumbs on top of the cake to simulate the dust on the monster truck obstacle course.
Cut off one third of the second sheet cake lengthwise. Trim the smaller piece with your knife to form the shape of the truck's hood and cab. (It should be half sloped and half flat. Use your monster truck image as a guide.) Take the remaining two-thirds of the second cake and place it atop of the cake you just frosted, relatively in the center, to form the truck's body. Frost this cake with vanilla icing, adding food coloring as needed to make it the color you'd like your truck to be.
Stack the piece you trimmed on top of the rest of the second cake with the sloped part facing to the left and meeting the left edge of the second cake exactly. Frost it with your remaining vanilla icing in the same color you just used.
Trace windows in your cab's icing using a toothpick. (Again, your truck image will help.) Draw four side windows, a back window and a windshield. Then cut your foil to match the areas you've traced. Place the foil on the cake for a shiny and almost glass-like look. (It will easily stick to the icing.) Put two to four marshmallows on top of the cab to form the monster truck's lights.
Place the donuts on the cake board and stick them to the body of your monster truck with your chocolate icing. The tires should overlap both the second cake and the first cake. Remember, they are pretty big on the real thing. Use your icing bag with tips to draw door handles, a bumper, a car number, flames or any other embellishments you would like on your cake.
Remove the aluminum foil before you eat the cake.