This is a Halo cake I made for my nephew's 14th birthday. This is my 3rd sculpted/3D cake. The head and torso are strawberry cake and the shoulders are Rice Krispie treats. It's all covered in marshmallow fondant and then detailed and hand painted (I don't own an airbrush, yet!) I piped the birthday message and Halo logo in buttercream.

Step 1: Supplies and Info Needed

Here's the list of supplies and info (recipes, etc.) you will need.

2 boxes of desired cake mix
All-purpose flour
Sour cream
Sugar
Salt
Eggs
Flavoring extracts (vanilla, almond, butter)
Mini and regular size marshmallows
Powdered sugar
Meringue powder
Crisco
Water
Rice Krispies cereal
Buttercream icing
Gel or other food colorings
Food-safe paint brushes
Rolling pin
Two 6" cake pans
Two 10" cake pans
Various tools for detailing the fondant (I use a set that was made for clay sculpting)
Knife to carve cakes
2 quarter sheet cake boards w/ foil to cover
Piping bag and tip #'s 1 & 3
Cake icing spatula
1 large plastic support dowel (can be gotten at Hobby Lobby and other places that carry a good selection of cake decorating supplies)

I use the WASC (white almond sour cream) recipe found here to make my cakes instead of using the box directions, as this recipe makes the cake a bit sturdier which is better for the sculpted/3D cakes: http://cakecentral.com/recipes/7445/the-original-wasc-cake-recipe

I use this recipe for the buttercream icing; I made one batch of this for this cake:

2 cups Crisco
2 lb bag of powdered sugar
4 tbsp meringue powder
2 tsp clear vanilla extract/flavor
2 tsp clear butter flavor
1 tsp clear almond extract/flavor
1/2 tsp salt
Water

Sift the powdered sugar and meringue powder together into a bowl.

In a small bowl or a measuring cup, put in all the flavorings/extracts and then add to that enough water to make the mix 1/2 cup. Add in the salt and stir until the salt is dissolved.

In the mixer bowl put the Crisco and water/extract mix. Beat on a medium-low speed for about 40 seconds, to just get it started mixing.

Next slowly start adding in your powdered sugar/meringue mix while mixing. Once it's all in there, mix on that same slow speed for about a minute.

The Rice Krispie Treats recipe can be found here and also on the side of the box of cereal; I made one batch of these for this cake:
http://ricekrispies.com/#/recipes/the-original-treats

I use marshmallow fondant because it tastes good, is easy to make and is also very inexpensive! I use the recipe found here and I made a triple batch of it for this cake:
http://www.wilton.com/forums/messageview.cfm?catid=7&threadid=137541&FTVAR_MSGDBTABLE=

Step 2: Bake and Stack the Cakes

Using the WASC recipe, make two 6" round cakes and two 10" round cakes. I used one box of mix with the recipe for each set of sizes (1 box for the two 6" and 1 box for the two 10".)

Once they are baked and completely cooled, stack the 6" cakes together with a layer of buttercream in between and the 10" cakes together with a layer of buttercream in between.

I then freeze the cakes for at least a few hours so that they are easier to carve (not as crumbly.)

Step 3: Carve the Cakes Into Shape

Once the cakes are frozen it's time to carve.

I print out lots of reference photos in as many angles as I can get and lay them out on the counter so I can see them while carving/shaping the cakes.

I carved the head first out of the 6" cakes. Once it was done I put it back in the freezer and took out the 10" cakes and carved the torso. Once that was done it was back into the freezer while I made the buttercream icing.

Step 4: Cover the Carved Cakes in Buttercream

Before starting the buttercream I got an old thin plastic bowl that I didn't mind destroying and I cut a hole in the bottom of it big enough to fit my plastic support dowl through. Then I pushed the plastic support dowel up into the head from the bottom, not going through the top of the head. Then I turned my bowl over and stuck the dowel through that hole I cut so that the head rested on the bottom of the bowl and the dowel was going down into the bowl. I did it this way instead of putting the dowel into the torso of the cake and then just pushing the head down onto the dowel later because I wasn't sure how much pressure that would cause on the head when pushing it down onto the dowel and I was afraid it would get smushed.

After making the buttercream icing I took the cakes back out of the freezer and covered them both in a thin layer (crumb coat) of buttercream. This gives the fondant a surface to stick to as it will not stick to the plain cake and to keep crumbs from going everywhere and it also seals int he moisture of the cake.

After applying the icing I give it about 20-30 minutes to set, or crust over and then I'm ready for fondant. I'm in Texas and it's summer so I actually put it in the fridge to set.

Cover your left over icing and set it aside to use on the shoulders and for the piping.

Step 5: Make and Shape the Rice Krispie Treats

Next make the Rice Krispie treats and then shape the shoulders to size and cover those in buttercream as well.

Step 6: Make the Fondant and Cover the Pieces and Detail

Next make the marshmallow fondant (or use store bought if you want and don't mind the not so great taste.)

I set aside a little bit of the fondant and left it white for the face mask area, neck area and the little triangle and chest lights details and colored the bulk of the fondant with the gel food coloring. I used black to get the dark purple color but you could use any color you want really. I think different characters in the game have different color armor. I was going with the Noble 6 character because that is the one my nephew liked the most. I couldn't find any metallic colorings so I just went with the colors I had.

Next I rolled out the fondant and started applying it to the cakes. I used a flexible see-through ruler to measure different areas of the parts I was covering and then cut out the shapes from the rolled out fondant and put them on the cake

When applying fondant over top other fondant that was already on the cake, all you need to use is a little water to stick it to the surface of the other fondant. I would brush it on the back of the piece I was applying with a food-safe paint brush.

Also cover the buttercream-covered Rice Krispie treat shoulders with fondant.

I detailed parts that needed it as I went along; using the clay tools and my fingers.

I also added a donut shaped piece of fondant as a neck, with a hole in the middle to allow for the plastic support dowel that was in the head to go down into the torso part of the cake when I put the head on.

Step 7: Paint the Parts and Put Them Together!

Next I painted the cake with the gel food colors mixed with vodka. The vodka is used because water will deteriorate fondant (makes it real sticky, which is why it's good to use to stick fondant to fondant.) The vodka also evaporates fast, leaving behind the color and no vodka so you don't have to worry about alcohol on your cake. :)

I painted the neck area black and used a less solid black in all the creases and in other areas. I used a light wash of yellow on the the face mask and triangle details and light blue on the little lights on the front of the chest.

Once the painting was done I put the head on the torso, guiding the support dowel that was sticking out of the bottom of the head into the hole of the donut in the neck area and down into the cake.

I put a little buttercream on the bottom of the shoulders and just stuck those in place on the board. They are not actually attached to the torso, just pushed in and the buttercream held them in place.

For the final touch I used the white buttercream and tip #1 to pipe in the "UNSC" on either side of the head and then colored the remaining buttercream and piped the birthday message with tip #3.

And then it was done!