Ginger-Chocolate Gradient Cake

When someone in my lab has a birthday it is the responsibility of the last person who had a birthday to make them a cake. The other girl in my lab (Andrea) and I both have December birthdays. Mine is so close to Christmas it always gets a little lost in all the other sweet treats and festivities. This year we decided a while ago that it would be fun to get together and make one big cake for both our birthdays and have it in between. Originally this was because we wanted to reprise our amazing rainbow cake for a big enough audience to eat it. But when it came to now we felt like doing something a little different. So we took two of our favourite things, ginger and chocolate, and stuck with layers (four this time) and decided to geek it up with a lab themed gradient (our lab does a fair bit of work on developmental patterning involving morphogen gradients).

For the cake (this quantity makes 4 fat layers):
(based on this recipe)
6 cups flour
2 cups finely chopped crystallised ginger

Both photos taken by Paul

4 tsp ground ginger
1 tsp bicarbonate of soda
1/2 tsp salt
1 1/2 cups (3 sticks) unsalted butter, room temperature
1 1/2 cups (packed) golden brown sugar
4 large eggs
2 cups plus 4 tbsp buttermilk
~1 cup cocoa powder

Inner icing:
3 tbsp butter
3 tbsp granulated sugar
3 tbsp water
3 scant cups icing sugar
2 tsp ground ginger

Outer icing:
12 oz 70% chocolate
1 cup hot water

Decoration:
Edible gold dust
Crystallised ginger, chopped

Heat oven to 350F. Grease four 8-inch round cake tins and line the bottoms with baking paper. Mix flour, crystallized ginger, ground ginger, bicarb and salt with a fork in a medium bowl. Beat butter and sugar in a separate, large bowl until light and fluffy. Add eggs one at a time, beating until well blended after each addition. Mix in dry ingredients alternately with buttermilk in three additions each, scraping down sides of bowl. Beat just until smooth.

Divide batter between four bowls and add cocoa or additional ginger so that each bowl has more chocolate and less ginger than the last: going from very gingery and no cocoa to very chocolatey and less ginger. Check the batters are of similar consistency, then put each into a separate prepared cake tin. Bake cakes until skewer comes out clean, about 30 minutes. Cool for 10 min then turn cakes out and cool completely.

For the inner icing, heat the water, granulated sugar and butter in a small pan, then add the icing sugar and ground ginger and mix until smooth. Allow to cool.

For the outer icing, melt the chocolate then add the hot water and beat until smooth.

To assemble, put the darkest layer on a plate and smear with 1/3 of the inner icing. Sprinkle with chopped crystallised ginger. Put the next darkest layer on top and repeat. Add the second lightest layer and spread with the last 1/3 of inner icing, then put the lightest layer on top. Dump the outer icing on top and use a straight-edged knife or palette knife to smear it all around the outside of the cake, covering the top and sides as evenly as you can. Use remaining preserved ginger and gold dust to make a decoration on top (we did a shooting star).


Could perhaps have done with more inner icing (think we're both of the less is more camp when it comes to icing in general). The outer icing was obviously basically just chocolate but I was into that. The cake was quite dense and heavy (I blame the buttermilk) so it added up to a massive piece of cake. If using this recipe I might have used 3/4 of the cake recipe quantity and split it in 4 still. Or used less batter and made more of a simple Victoria sponge (my original thought) with added ginger / cocoa, just putting the preserved ginger between the layers and on top - would be lighter.