Fish Tank Cake

I tend to get a little carried away with my baking ideas. This was definitely one of those ideas. A's birthday was coming up and I decided to make a tropical fish tank cake for his birthday. He recently inherited a real fish tank, and it has become his new favourite hobby. His only request, when I asked him what type of birthday cake he wanted, was that it be chocolate. This did not satisfy the crazy baker within, so I started to brainstorm a little.

My Mum used to bake the most amazing, adorable birthday cakes for us when we were growing up. Most of them came from the Women's Weekly Birthday Cakes cookbook that everyone in Australia owned in the 80's, and I used to LOVE flicking through the book and pointing out my favourites to my Mum. I always wanted the kitchen cake, with its little stove top and mini plastic frying pans with bacon and eggs made out of lollies. Lucky for me, I managed to save this cookbook. During my brainstorming, I was flicking through it and the swimming pool cake caught my eye. The top of it was filled with green jello, and I've always thought that was an awesome idea. So I decided that I would make A a tall, rectangular triple layered chocolate fish tank birthday cake, topped with blue jello and decorated with sugar cookie fish.

I knew this was going to be exhausting. I had to bake the cakes, set the jelly, cut out and bake and then ice the sugar cookies, make a ton of buttercream and then put all the elements together. I was perfectly aware of the fact that this project would be a million times easier if I just decorated the whole thing using fondant rather than buttercream and sugar cookies, but I hate fondant. It might look pretty, but it tastes like toothpaste. And I wanted something we would actually want to eat.

The whole process took about three separate days of preparation. Since his birthday was in the middle of the week, I had to bake the sugar cookies and the cake on the nights before, and then on his actual birthday I iced the cake and the cookies. It took SO much longer than I expected to decorate, and it also reminded me of the fact that I suck at decorating. The icing refused to go on smoothly at first, thank god I finally invested in a palette knife or it would have been even messier. Decorating sugar cookies is fiddly and hard and I made a total mess of it. After icing about 4 cookies and managing to spill black icing on the carpet, I gave up. So if you're wondering why you only get to see one side of the fish tank cake, that's why. I gave up and stuck fish shaped gummies on the rest of the cake. And I forgot to add the little silver cachous that were supposed to look like bubbles around the tank. What can I say, it's a little rustic. Oh well. And please excuse the very average photos, it was about 6pm when I finally gave up and there wasn't much light around :(

But A did love the cake. And it tasted pretty good too. I used a chocolate cake recipe from Ina Garten which turned out beautifully moist and rich, but I substituted it with my own chocolate buttercream which was a bit stiffer because I was scared that the cake might collapse under its own weight. The buttercream went really well with it though, deliciously chocolatey without being too rich. I got a great tip to use Martha Stewarts sugar cookie recipe from Not So Humble Pie (her science sugar cookies are AMAZING, I am in total awe), and they kept their shape perfectly and were super tasty. I'll definitely be using both recipes again, hopefully for something a little less insane. Oh and the weirdest part? The jello actually tasted pretty good with the cake! It was a HUGE cake, since it was the size of about 3 small loaf tins stacked on top of each other. so we have a lot of leftovers. But I imagine it would be great for a children's birthday party, and I'm sure there are many people out there who could do a much better job with the decorating than I did. But it was a fun challenge for myself, and the important thing was that the birthday boy was happy. Happy Birthday A!

Fish Tank Cake
(adapted from Ina Garten's Beatty's Chocolate Cake recipe & Martha Stewart's Sugar Cookie Recipe, will feed a large group)
For the chocolate cake:
Butter, for greasing the pans
1 3/4 cups plain flour, plus more for pans
2 cups sugar
3/4 cups good cocoa powder
2 teaspoons baking soda
1 teaspoon baking powder
1 teaspoon salt
1 cup buttermilk, shaken
1/2 cup vegetable oil
2 extra-large eggs, at room temperature
1 teaspoon pure vanilla extract
1 cup freshly brewed hot coffee

Preheat the oven to 180 degrees C. Butter 3 small loaf tins. Line with parchment paper, then butter and flour the pans.

Sift the flour, sugar, cocoa, baking soda, baking powder, and salt into the bowl of an electric mixer fitted with a paddle attachment and mix on low speed until combined. (I don't have a paddle attachment but my regular hand mixer worked fine) In another bowl, combine the buttermilk, oil, eggs, and vanilla. With the mixer on low speed, slowly add the wet ingredients to the dry.

With mixer still on low, add the coffee and stir just to combine, scraping the bottom of the bowl with a rubber spatula. Pour the batter into the prepared pans and bake for 35 to 40 minutes, until a cake tester comes out clean. Cool in the pans for 30 minutes, then turn them out onto a cooling rack and cool completely.

For the chocolate buttercream:
180g semi-sweet chocolate, melted
200g butter, softened
Approx 3 cups icing sugar, sifted

Beat butter with an electric mixer on high speed until fluffy. Add icing sugar and continue to beat until combined. Gradually add melted chocolate to the mixing, while continuing to beat, until the mixture is smooth.

Place one cake layer, flat side down, on a flat plate or cake pedestal. With a knife or offset spatula, spread the top with buttercream. Do the same with the next cake layer and then place the final cake layer flat side up on the top. Use buttercream to ensure all the sides of the cake layers line up nicely. Place in the fridge to chill for an hour, or you can leave it overnight, covered in cling film.

For the exterior buttercream:
250g unsalted butter, cubed
250g icing sugar, sifted
1 tsp salt
Blue & Black food colouring

When you are ready to ice the outside of the cake, beat the unsalted butter in a large mixing bowl with salt until it is smooth. Gradually add icing sugar, one cup at a time, beating until combined. I used about 80% of the icing with blue colouring, spreading it over all five sides with a palette knife. The rest was mixed with black food colouring to pipe around the edges.

For the sugar cookies:
4 cups sifted all-purpose flour
1 teaspoon baking powder
1/2 teaspoon salt
225g unsalted butter, room temperature
2 cups granulated sugar
2 large eggs
2 teaspoons pure vanilla extract

Sift flour, baking powder, and salt into a bowl. Place butter and sugar in the bowl of an electric mixer fitted with the paddle attachment. (Once again, I didn't have this but it works fine with a regular hand mixer) Mix on medium speed until pale and fluffy. Mix in eggs and vanilla. Reduce speed to low. Gradually mix in flour mixture. Divide dough into quarters; flatten each quarter into a disk. Wrap each in plastic. Refrigerate until firm, at least 1 hour or overnight.

Preheat oven to 170 degrees C with racks in upper and lower thirds. Let one disk of dough stand at room temperature just until soft enough to roll, about 10 minutes. Roll out dough between two pieces of plastic wrap to 1/4-inch thickness. Remove top layer of plastic wrap. Cut out cookies with a 4-to-5-inch cookie cutter. (I used a knife to carve out the shapes for my fish) Transfer cookie dough on plastic wrap to a baking sheet. Transfer baking sheet to freezer, and freeze until very firm, about 15 minutes. (I actually skipped this step since I had no room in my freezer and it still worked fine) Remove baking sheet from freezer, and transfer shapes to baking sheets lined with nonstick baking mats. Roll out scraps, and repeat. Repeat with remaining disk of dough.

Bake, switching positions of sheets and rotating halfway through, until edges turn golden, 15 to 18 minutes. Let cool on sheets on wire racks.

For the royal icing:
1 large egg white
2 cups icing sugar, sifted
Food colouring

Beat egg white with an electric beater until soft peaks form and then gradually add the icing sugar and beat until combined. Split into separate bowls and add food colouring as needed. Pipe onto sugar cookies using a piping bag and leave to set on a wire rack for half an hour. Decorate cake with sugar cookies and other lollies. I suggest mini marshmallows for sea anemones, and silver cachous for bubbles.

Use a small spoon to dig out a shallow layer off the top of the cake and fill the top with blue coloured jello. (You will have to prepare this the night before). You do end up with a little bit more icing that people would want to eat on a cake, so feel free to slice away some of the exterior icing before serving up slices.