Volcano cake…
Recently I asked my best friend Andrew what he thought of Cakeophilia and he responded with praise but pointed out that it was missing one major feature.
One of geological proportions.
You might have seen the Earth and Jupiter cakes that a fellow sciency cake lover has made. But she’s not the only one who translates geography into cake.
Meet… Mt Ruapheu, NZ.
Ruapheu Cake in its natural habitat
You see, Ruapehu is a stratovolcano. It is composed of layers of lava and tephra that has built up over successive eruptions to create the 2796m of volcano in the centre of New Zealand’s North Island that happy tourists see today. And in winter, it’s covered in snow and Andrew and I like to ski on it.
On the other hand, birthday cake is composed of layers of cake and buttercream and is covered with a drift of frosting. And Andrew and I like to eat it.
It’s obvious when you think about it.
Ruapehu has three ski fields, the very large Whakapapa, quite large Turoa and teeny weeny Tukino.
Ruapehu Cake
And it has a penchant for lahar, a torrential river of heated mud and rocks which has been known in the past to destroy railway bridges and flow through (luckily empty during the 1995 eruption) ski lift queues.
Because of the crater lake, lahar will precede any lava eruption, and mud is brown, like chocolate. Hot lava on the other hand is red… Like raspberry coulis.
And snow is light and fluffy like marshmallow frosting. And igneous rocks are dark and crack like chocolate.
Volcano cake. It’s obvious really.
So a while back, for Andrew’s birthday… The geologically correct… Interactive Ruapehu cake.
Interactive Cake Instructions
Here are the ski fields:
Ruapehu Cake – Whakapapa Skifield
Ruapehu Cake – Turoa Skifield
Ruapehu Cake – Tukino Skifield
Here is the crater:
Ruapehu Cake – Crater Lake
And here is a Birthday-boy eruption sequence….
Ruapehu – Fire Fountain
With fire fountaining, chocolate ganache lahar and raspberry lava…
Chocolate Ganache Lahar Flow
Raspberry Lava commences…
Eruption Complete!
It’s hard to know what’s better… A volcano cake all sauced up…
Aerial Erupted Volcano Cake
Or cut…
Sectioned Andesite Volcano Cake
…to reveal a true andesitic stratovolcano, complete with eruption tube, lava chamber and layers of chocolate cake basalt and chocolate crumb buttercream tephra.
Inside the Ruapehu Cake
So how did I make it? Not as hard as you might think!
Volcano cake:
for the cake:
One 20cm kugelhopf ring tin (these are shaped like a wide, fluted cone, with a narrow tube in the centre. You could use a regular ring tin or bundt tin but you will need to carve the cake into a cone and your volcano will look more like a Kilauea than a Fuji)
One quantity of Best Chocolate Mud Cake
One quantity of Basic Buttercream
One quantity of Marshmallow Frosting
Assorted chocolate bars, including Cadbury Dairy Milk, Flake, and Snickers.
Approximately 1 cup of shredded coconut, for sprinkling
Approximately 2 tbsp of cocoa, for sprinkling
Approximately 1tbsp white sugar, coloured blue with a drop of blue colouring.
for the eruption
Five (or more) white birthday candles
200mL chocolate ganache
200mL raspberry coulis
make the cake:
Grease (with butter) and flour the kugelhopf tin. Set aside.
Mix the chocolate mud cake, spoon into the tin, smooth the surface, and bake until a skewer inserted into the center comes out clean. It will rise up a lot and the surface won’t be flat, don’t worry about that.
When the cake has cooled slightly, turn out onto a wire rack.
While the cake is baking make the ganache, coulis and buttercream. Keep the buttercream at room temperature; the rest can be refrigerated until needed, but if you want to make the cake a week in advance it’s best to make it closer to the serving time!
With a serrated knife, trim the cold cake so that it has a flat base to sit on. If there is enough cake that has risen above the tin, cut a 1.5-2cm layer to act as the base for the volcano. Put the trimmed cake back into its tin.
Take the trimmings from the cake and crumble them up into 1-2mm crumbs (some will be coarser) Reserve 1/4 of these crumbs (including the coarser ones) for decorating the cake. Tip the rest into the buttercream and stir til well combined.
Now it’s time to layer the volcano cake. You need to cut concentric cones, so this takes a steady hand to master!
Cut the first layer approximately 1.5-2 cm from the edge of the tin. Insert a long sharp knife straight into the cake in the same angle as the slanted side of the tin, all the way to the inner tube of the tin. Using a slight sawing action, and keeping the knife in the same angle, slowly rotate the tin while cutting until you have cut all the way around. Don’t worry if it’s not completely straight, volcanoes aren’t perfect!
Repeat this process another 1.5-2 cm in from the first cut, and continue until you have cut approximately four layers.
assemble the cake
Place the round flat cake base in the center of a large serving platter or cake board (preferably 40-45 cm diameter’ and use a serving platter with a lip around the edge if you don’t want the drama of lahar on the table!). Using an offset spatula or flat knife, coat the base with a half-centimeter layer of crumb buttercream.
Ease the innermost cake “cone” from the tin and place coat the cone with a half-centimeter layer of crumb buttercream, leaving the lava tube empty. Gently ease the second cake layer over the top. Don’t worry if it splits…. Volcanoes aren’t really round! chasms can be built up as a feature if desired. Repeat with the rest if the cake and buttercream, ending with a layer of buttercream. Use any excess buttercream to build up the peak of the volcano. Refrigerate until very cold. At this stage the cake can be wrapped in cling film and will keep for up to a week in the fridge (so you can make it one weekend and decorate it the next ready for a Saturday night eruption!).
On the day of serving the volcano cake (or the day prior), make the marshmallow frosting.
For the lower slopes of the volcano cake, recreate the snow line. Combine coconut and cake crumbs and sprinkle heavily over the lower part of the cake, gradually decreasing in density as you ascend. Add more chocolate “rocks”. Dust the lowest regions with cocoa powder.
Coat the upper slopes of the volcano cake with frosting, sculpting the frosting to create ridges and crevasses as desired. If you don’t have a favourite volcano, google some topographical maps for inspiration! Put a 2-3 cm plug of frosting in the top of the eruption tube, and create a hollow for the crater lake. Sprinkle the blue sugar into the crater lake. Gently press the white birthday candles deep into the cake all around the crater lake, so that the wicks and a couple of millimetres of each candle extends above the frosting.
Decorate the ridges with chocolate and cake crumb “rocks” of you choice.
serve your volcano!
When you’re ready to serve the volcano cake, make sure that your ganache is slightly warm so that it will pour well. Light the candle wicks around the crater and slowly pour all the ganache into the crater. Follow with all the raspberry coulis. The ganache and coulis will put out the candles! Remember to pull them out before you slice the volcano cake for serving.
Enjoy!xxx
