The Cake Slice July 2010: Key West Cake with Mango Mousse and Ginger Lime Cream

I was really excited when this cake got chosen as this months Cake Slice cake. It’s one I had been longing to bake for ages, the ingredients sounded so fresh and tropical – mango, fresh ginger and lime – and yet it is not a combination I have together in a cake before. The cake also called for a rum syrup to be drizzled over the cake layers before assembly which just made it appeal even more.

The cake requires quite a bit of work due to its many components – cake, rum syrup, mango mousse and ginger lime cream. The ginger lime cream also calls for you to make your own ginger lime curd which may sound a bit of a nuisance but I can assure you the results are completely worth the extra effort. In fact this curd turned out to be my favourite part of the cake, so much so that I plan on making it again and eating it just as curd. It was so fresh and zingy with the lime zest and juice and the ginger was just subtly there in the background, delicious. We were meant to pass the curd through a fine sieve to remove the zest once cooked, but I decided to skip this step as I liked seeing the green zest speckled through the curd, so pretty. Plus, I’m sure it added to the flavour.

The cake layers contain very little butter and the main volume of the cake comes from whisking eggs and sugar over a pan of hot water until ribbons form. This produces and very light and airy cake which has a springy bounce when pressed. The batter was quite thick and sticky and reminded me strongly of choux pastry dough.

Using rum syrup to soak the cake layers kept them wonderfully moist and added a lovely tropical flavour against the mango and lime. If you didn’t want to use alcohol I’m sure replacing this with pineapple juice would be equally tasty.

The mango mousse called for gelatine to help it set firm. Being a vegetarian I left this out completely and just replied on chilling the whipped cream mixture to help my cake set. I know you can get vegetarian style gelatine, but when you have lots of whipped cream I always think this is unnecessary. Plus, I don’t like the jellied texture it gives. Setting the cake in the fridge for a while does the same sort of job, as the cream firms up as it cools.

Overall I adored this cake. It was light, fresh and fruity, perfect for this time of year and I had fun learning some new techniques along the way. Click here to see my fellow Cake Slice bakers and their cakes.

Key West Cake with Mango Mousse and Ginger Lime Cream

Recipe from Sky High Irresistible Layer Cakes by Alisa Huntsman and Peter Wynne

Cake

6 eggs

225g caster sugar

1 tsp vanilla extract

300g plain flour

45g unsalted butter, melted and slightly warm

Rum Syrup

55g caster sugar

110ml water

55ml rum

Mango Mousse

350g finely diced mango (use tinned if fresh is not available)

75ml water

75g plus a separate 20g caster sugar
2 tsp unflavoured gelatine powder
2 tbsp light rum
225ml double cream

Ginger Lime Cream
4 egg yolks
110g caster sugar
Zest of 1 lime
55ml freshly squeezed lime juice
1 tbsp grated fresh ginger
330ml cold double cream

Cake Method

Preheat the oven to 180C. Line the base of three 8inch round pans with parchment or waxed paper.
Place the eggs in a large heatproof bowl. Gradually beat in the sugar and the vanilla. Set over a pan of simmering water and whisk constantly until all the sugar dissolves and the eggs are warmer than body temperature. Remove from the heat and, with the mixer on medium high, whip the eggs until very fluffy and stiff enough so that a slowly dissolving ribbon forms from the dripping batter when the beaters are lifted.
Sift the flour and return to the sifter. Carefully sift about a third of the flour over the top of the eggs. Using a rubber spatula, gently fold it in. Repeat with the remaining flour, folding just until blended evenly. Finally, drizzle the butter over the batter and carefully fold it in. Divide the batter among the 3 cake pans.
Bake the layers for 12 to 14 minutes or until a cake tester comes out clean. Transfer to a wire rack and let the cakes cool completely in their pans. To unmold, run a blunt knife around the rims to carefully release the edges of the cakes and tap them out gently. Carefully remove the paper on the bottom of each layer.

Rum Syrup
Combine the sugar and water in a small saucepan. Cook over a medium heat, stirring to dissolve the sugar. Boil until the syrup is reduced by half, about 110ml. Remove from the heat and add the rum.

Mango Mousse

Place the mango chunks in a medium nonreactive saucepan. Add the water, bring to a simmer and cook, stirring occasionally, until soft, about 10-15 minutes. Remove from the heat and let cool to room temperature.
Transfer the cooled mangoes, along with any liquid, to a blender or food processor. Puree until smooth. Remove 120ml of the mango puree, stir in 20g of sugar and set aside to use as garnish. Place the remaining mango puree (about 220-250ml) in a large bowl.
Put the gelatine in a small glass or ceramic dish. Add the rum and let soften for about 5 minutes. With a microwave on low, heat the gelatine until dissolved, about 10 seconds.
Whisk the gelatine and remaining 75g sugar into the mango puree until all the sugar dissolves.
In another large chilled bowl, whip the cram until stiff. Using a rubber spatula, fold the cream into the sweetened mango puree.

Ginger Lime Cream

Whisk the egg yolks in a small, heavy nonreactive saucepan. Gradually whisk in the sugar, then the lime zest, juice and ginger. Cook over a medium low heat, stirring and scraping the base of the pot with a spatula, until the yolks visibly thicken, about 3-5 minutes.
Strain through a fine mesh sieve to remove the zest and ginger chunks. Cover the ginger lime curd with plastic wrap, pressing it directly into the surface and refrigerate until very cold, about 1 hour.
In a large mixing bowl, whip the ream until stiff. Fold the whipped cream into the ginger lime curd.

To Assemble

Place one cake layer on a cake stand, flat side up. Soak it with 55ml of the rum syrup. Spread half the mango mousse over the layer evenly. Repeat with the second cake layer using another 55ml syrup and the remaining mousse. Add the last cake layer, soak with the last of the rum syrup and chill the cake for about 1 hour.
Once firm, frost the cake with the ginger lime cream. Use a pastry bag fitted with a star nozzle to decorate the cake with the remaining cream. Serve the cake with a spoonful of the reserved mango puree from earlier.