This Homemade Shark Birthday Cake Idea is a composite of every shark cake on this site. Thank you all for such wonderful advice and tips and pictures. The coolest thing I discovered from this venture was that I can make virtually any shape, given enough cake. The early picture of the raw carving could be the beginning of a car, a plane, a shark, with a little imagination and planning, stacked pound cakes will allow any shape to be carved.
My advantage was that I have a huge, almost empty freezer right now, which allowed me to easily freeze this between steps. Make sure you have the space to freeze your cake during this process. My disadvantage was that the body of the cake was HUGE and I could not possibly roll out a big enough piece of fondant to cover it without seams.
Here is my shark cake made from 3 sheet (pound) cakes baked in a 14" x 10" pan. Buttercream icing between the layers and on the outside, followed by fondant, painted mouth and gills, and gum paste teeth. The trick was starting a week early, and doing a little bit each night. I felt safe returning it to the freezer with just a loose wrapping of waxed paper.
Every single step was followed by a deep freeze. In order:
Bake 3- 14" x 10" sheet cakes (drop time to about 30 baking minutes as it is so thin). They will only be an inch high, but do not despair. Freeze hard with waxed paper in between.
Cut each in half to ~7" x 10" (they will be ~ 13" x 10" due to shrinkage).
Stack and frost in between with buttercream icing and freeze, covered in waxed paper.
Make the cuts shown in the side view FIRST, because you need those for fins. Use a serrated bread knife to saw off fins. Then look down at the cake from above and trim the left and right sides to your liking.
Shape mouth last. Refreeze. Brush off crumbs and drizzle with lightly-microwaved icing on the "raw" cut parts to glue any loose crumbs down. Refreeze.
Cover all parts generously in 2 small cans white buttercream frosting, put in freezer uncovered until hardened (a couple hours). Wrap individual pieces loosely in waxed paper and freeze hard. Reserve a 1/4 can frosting for fixing mishaps later.
I used one MMF recipe (from 16 oz-marshmallows and 2 lbs-powdered sugar) of blue-dyed fondant for the body (only add Crisco to your hands and rolling pin, or it gets too shiny and gross). I should have mixed the blue dye in at the onset, it ended up marbelized due my my inferior finger muscles trying to add it after incorporating the sugar.
Take pieces out of freezer one at a time and smooth down the ridges of the buttercream (full disclosure, I used my finger, but there is probably a more sanitary way to do this). Bad holidays will show through fondant.
I could have fondanted the fins without seams, but I was in a hurry, and used my pasta maker for the fins first (6" widths, but saved me a lot of rolling). I tried to cut seams at the edges to keep it neat. Lastly, I fondanted the body. I just simply could not roll out a big enough piece of fondant for it, so there is a seam on one side.
Freeze for a couple hours.
Fix up your buttercream icing boo-boos (you are happy now that you saved that 1/4 jar in the beginning). Save a few tablespoons, because you are going to make a few more mistakes.
Final touches are painting the inside of the mouth red, gum paste teeth (make these a day ahead so they are dry--soggy teeth are a nightmare), M&M eyes (with gum paste highlights), pressed and painted gills, and assembling the fins. Dorsal fin needed a Popsicle stick, but in retrospect, I should have cut a little square in the top of the shark's back to inset the fin squarely.
Voila! A Homemade Shark Birthday Cake Idea came together.
Materials--$35 (Assuming you have no Wilton's dyes on hand) Time--One week of 10-minute daily tasks to cook/assemble. Four hours to decorate with fondant and add details the day of the party. Faces on the soccer team as they simultaneously bit into it like sharks--Priceless!