Chocolate Truffle Cake Recipe: It's Spring!

It's officially the start of spring. 

By the sides of the roads, the tell-tale pink bloom of the occasional cherry blossom tree breaks up the symmetry of green and umber. An occasional chilly breeze still sweeps across the streets, bringing with it the last vestiges of winter, but there's no doubt in anybody's mind that spring has arrived. 

Picture by R

On the home front, I'm just about to wrap up a pleasant six weeks in Maroondah Hospital. After spending most mornings getting plied with coffee and pastries by several consultants, a small guilty voice in my head started to remind me that a little reciprocation is only right. I was a little cautious about bringing in an untried recipe, and so I turned to the classic hand-shaped chocolate truffles recipe from Alice Medrich. The recipe made plenty of chocolate truffles, and on a sudden whim, I turned the remaining chocolate truffle mixture into a cake. Say wha?

It's true, and what a result! Well, I can't claim credit for this idea; I recently bought Luxbite's Epic Chocolate Cravings, and I thought the chocolate layer tasted remarkably similar to chocolate truffles. So I gave my idea a whirl, and was pleasantly surprised at how good it looked - and tasted. 

This deceptively fancy-looking cake could not have been easier to do; it's even easier than making the original truffle recipe. There's none of that cutting, moulding, shaping or coating to do. Just pour the truffle mixture over a chocolate-graham base and let chill and voilà! a cake is ready to be sliced up and served. 

Chocolate Truffle Cake Recipe

Makes a 8.5 x 8.5 inch cake
Inspired by Luxbite's menu. Recipe adapted from Alice Medrich's Sinfully Easy Delicious Desserts 

I made a few changes to the original truffle recipe. For her truffles, Alice Medrich advised using chocolate of less than 62% percentage. I assumed it was meant to make the truffle body sweeter and balance the contrasting bitterness from rolling the truffles in cocoa powder afterwards. For this cake, as only the top is coated with cocoa powder, I think using chocolate with a higher percentage (but no more than 70%) helps bring the sweetness-bitterness ratio back to balance. The chocolate-graham base recipe was given to me by Karen Z.   

Ingredients
200g chocolate digestive biscuits, finely crushed
50g unsalted butter, melted 

2 large egg yolks, at room temperature
450g (1 pound) semisweet chocolate (about 65-70% percentage cacao), coarsely chopped
140g (5 ounces) unsalted butter, cut into small pieces
1/8 teaspoon salt, preferably fine sea salt
 115g (1/2 cup water), boiled

Unsweetened cocoa powder for dusting
white chocolate, shaved (optional, for decoration)

You Will Need
A strainer
A food processor, or a handheld blender
8.5-inch square baking pan, preferably with a removable bottom, or else lined with foil on the sides and bottom

Steps
1) Preheat the oven to 180C. Combine the chocolate digestive biscuits and the melted butter. Pack the bottom of the cake pan firmly with the crushed biscuits-butter mixture and bake for about 10-15 minutes. Set aside and let cool. When the cake pan has returned to room temperature, brush the sides of the cake pan with butter (to ease the removal of the chocolate cake afterwards). 

2) Put the egg yolks in a small metal container, and place the container into a larger bowl filled with warm water, until the yolks are slightly warm. 

3) Melt 140g of butter in a medium-sized saucepan over the smallest flame on the stove. When all the butter melted, add chocolate and salt. Stir continuously until the chocolate has melted, taking the saucepan away from the fire for brief periods of time if you're afraid the chocolate might burn. Remove from heat once the chocolate has melted and mixture is warm, about 49-55 C. (Alice suggests using a double boiler, but I always used this direct flame method for heating chocolate+butter and never had a problem before. Plus less stuff to wash = win.)

3) Bring 1/2 cup of water to boil, and let cool a little. Pour the just-boiled water in a steady stream into the 2 egg yolks, stirring constantly to prevent bits of the egg from cooking. The final temperature should be at least 71C (160F). 

4) Place a strainer over the chocolate mixture and pour the egg mixture into the chocolate. Tap the strainer against the bowl to let the more-fluid egg mixture through, but do not press on the cooked eggs. Stir the mixture well.  

5) Pour the mixture into a food processor (make sure not to overfill!) and pulse for a few seconds. Scrape down the sides of the food processor, and blend again for 20-30s, or until the mixture becomes smooth, like a chocolate pudding. Scrape the mixture into the prepared pan and let come to room temperature. Then cover and refrigerate until firm, for at least a few hours.

NotesTo crush the digestive biscuits, pound a few biscuits at a time in a plastic bag until the biscuits become finely crushed and no big chunks can be seen. 

I haven't tried it for myself, but it seems that regular digestive biscuits can be used together with melted chocolate (maybe about 25g?) and melted butter.