A good chocolate cake

Some days I just want chocolate cake. Not a fondant cake, or a mousse cake, or a runny-centered cake, or even a Carrément chocolat cake from Pierre Hermé in Paris, but a good old-fashioned sponge cake. Yesterday was one of those days. I was entertaining six five-year-olds for Sam's birthday with a picnic in the Parc du Château, and it was in my interest to keep the chocolate/sugar rush to a minimum. Last year I had started tinkering with a recipe in one of my many hundreds of cookbooks to make it just right for such an occasion, so I decided to fine-tune it to create a reliable cake that I could turn to at short notice.
The original recipe, from a book called The Uncommon Gourmet by Ellen Helman (Ten Speed Press) that followed me across the world from Canada, called for sour cream, an ingredient I can't find in France. Crème fraîche works well (when doesn't it?) but this time I decided to use yaourt à la grècque, a creamy, sour yogurt sold in any French supermarket. The closest I can come to unsweetened chocolate is Lindt 99%, which is sneakily sold in packets that contain a huge amount of plastic packaging and a tiny amount of chocolate, so I opted for the brown-paper-wrapped Nestlé dessert, which contains 52 per cent cocoa solids and zero snob appeal. To compensate for the sweetened chocolate, I reduced the sugar and added a little cocoa powder to the recipe. Light brown sugar brings a slight caramel flavor to the cake. The longer I live in France the less I feel inclined to make fluffy frostings, so I glazed and filled the cake with ganache. Ganache, in case you're wondering, is French for "ridiculously easy yet oh-so-chic."
I was pleased with the result: the cake was chocolatey without being too intense for undeveloped chocolate palates, with a layer of cherry jam in the center providing a little fruity contrast. But the real test would be Sam, who traumatized me on his third birthday by declaring the cake that I had so lovingly made to be "a little dry." That was not a risk with this cake thanks to the yogurt and this time he had only one thing to say: "Encore."

A good chocolate cake
Serves about 16

1 cup sour cream or Greek-style yogurt
1 tsp baking soda
3 oz good quality dark chocolate (80 g)
1 cup butter (100 g)
1 1/2 light brown sugar (300 g)
5 free-range eggs
1 tsp vanilla (5 ml)
2 1/2 cups flour (325 g)
2 tbsp cocoa powder (30 ml)
1/2 cup cherry jam (125 ml)
Sprinkles, for the decoration

Milk chocolate ganache:

4 oz good quality milk chocolate (100 g)
1/4 cup whipping cream (50 ml)

Dark chocolate ganache:

8 oz good quality dark chocolate (200 g)
1/2 cup whipping cream (125 ml)

Preheat the oven to 350 F (160 C). As always when baking, I used the convection setting at a slightly lower temperature. Grease and line a 9-inch cake tin with a removeable base, or two 9-inch layer tins.

Stir together the sour cream or Greek yogurt and baking soda and set aside at room temperature.

Melt the chocolate in a heavy pan over very low heat or in a double boiler (if I had a microwave, I might use it here). As soon as it's melted, set it aside to cool.

In a mixer (I used my beloved KitchenAid), beat together the butter and sugar until fluffy. You'll need to scrape down the sides of the bowl once or twice with a rubber spatula. Add the eggs one by one, mixing well after each addition. Mix in the cooled chocolate and vanilla.

Sift together the flour and cocoa, or at least sift the cocoa, which is all I did. Fold the flour mixture and sour cream alternately into the egg mixture, beginning and ending with the flour. When the batter seems smooth, pour it into the tin(s).

Bake layers for about 25 mins, and a bigger cake for about 45 mins, until the top of the cake feels slightly springy to the touch.

Remove the cake(s) from the tin(s) and set aside on racks to cool.

For the milk chocolate ganache, break the chocolate into pieces in a small bowl. Bring the cream to a boil and pour over the chocolate. Allow to rest for about 30 secs before stirring with a small whisk until the mixture is smooth. Follow the same procedure to make the dark chocolate ganache and set both ganaches aside at room temperature.

When the cake is cool, cut in half if necessary. Spread the cherry jam over one layer and pour the milk chocolate ganache, which should be thick but still a little runny, overtop. Top with the second layer, then spread the dark chocolate ganache all over the cake using a palette knife. It's a good idea to place the cake on a rack over a large plate while you're doing this, to catch the dripping ganache. If you're making this cake for a child's birthday, top with sprinkles or other decorations. Place in the refrigerator until the ganache sets.

There is of course nothing to stop you from making only one kind of ganache, dark or milk chocolate.