Step 1: Bake Your Cake.
Let your cakes cool completely before frosting them. After your cakes come to room temperature, I recommend putting them in the freezer for at least a couple hours to make it easier when shaping/cutting them.
Step 2: Begin Shaping Your Cake.
Step 3: More Shaping.
You will want to find something round you can use as a guideline that will still leave the edges fairly thick (so they don't break on you during assembly); I would recommend a round cookie-cutter, although I used a child-sized bowl.
You will now have three sections of cake:
- A solid 9" round section, which will be the base of your cauldron,
- A hollow 9" round section, which will be the top of your cauldron,
- And a small round section, which will be the base of your witch's hat.
Step 4: Ready Your Frosting and Gather Your Icing Supplies.
Make, or purchase, approximately 4lbs of buttercream icing. (There are many bakeries that will sell you the icing they use if you are uncomfortable making your own.)
(If in doubt, more icing is better than not enough.)
Divide the icing, and color as follows:
- slightly less than 3lbs will be brown
- slightly more than 1lbs will be green
Two bags, a spatula, an icing tip, and one or two large round tips (I used one round tip and simply washed it between colors).
Step 5: Ice Your Cake.
To get more of rustic texture, place a piece of wax paper on your cake and smooth it down with a clean spatula. Lift the wax paper off and repeat around the cake.
Step 6: Cauldron Bubbles.
You can achieve this by holding your bag straight up-and-down, applying enough pressure to create a circle, and lifting the bag away after releasing the pressure.
Step 7: Witch's Hat.
You will begin by angling off the top of your small circle of cake, like you did in step two (but slightly more drastic).
Ice the cake with the brown icing as you did for the cauldron (remembering to use your spatula to "push" the icing onto the cake).
Then use your spatula to ice the cone in brown as well, and gently push the cone onto the top of the cake.
Step 8: Cauldron Handles.
Using your brown icing and your round tip, create handles for your cauldron. This can be any sort of "U" shape, as long as you make sure to start and end your "U" over the curve of the edge of your cake (so your handles don't fall off on you).
I also used my round tip to cover the seem on the hat, where the cone and cake meet, to make it easier to apply candy decor.