How I Actually Make a Black Forest Gateau
The James Martin version is one of the more straightforward take on this cake. He keeps it honest instead of overcomplicating things with obscure techniques. I've made this probably a dozen times over the years, usually when someone asks me to bring dessert somewhere. It's reliable if you pay attention to the layers. You'll need a chocolate sponge, kirsch-soaked cherries, whipped cream, and dark chocolate shavings. That's essentially it. James Martin's recipe calls for something like 200g dark chocolate, 200g butter, 200g sugar, and six eggs for the sponge. Three 20cm tins. The cherries are jarred in kirsch — don't skip the kirsch. Using regular cherry syrup just tastes like sweet jam and ruins the whole point. The cream should be double cream whipped to soft peaks. Not stiff. If you whip it past soft, the cake becomes a dairy brick and nobody wants that. I learned that the hard way once.
Method, In Practice
Start by melting the chocolate and butter together. Double boiler works, but I find a heatproof bowl over a pan of simmering water gives you more control. Don't let the water touch the bottom of the bowl or you'll risk curdling the chocolate. Separate the eggs. Whisk the yolks with the sugar until it goes pale and thick, about four minutes by hand or two in a mixer. Fold in the melted chocolate. Then fold in the egg whites, which you've beaten separately to soft peaks. Divide between the three tins lined with parchment. Bake at 170°C for about 20 to 25 minutes. A skewer should come out clean. The cakes will pull away from the sides slightly when they're done. Turn them out onto a wire rack and leave them to cool completely before you even think about assembling. Warm sponge tears apart when you try to soak it with syrup. Just wait. While the cakes cool, drain the cherries and reserve the liquid. Mix the reserved liquid with a bit of kirsch — maybe a tablespoon if the jar liquid isn't boozy enough — and brush it onto each layer. This keeps the sponge moist and gives it that distinct flavor. James Martin doesn't always stress this step enough, but it matters. Dry Black Forest cake is sad cake.
Whip the cream. Spread a layer over the first sponge, then top with cherries. Repeat for the second layer. The third layer goes on top, flat side up. I usually cover the whole thing with the remaining cream, then chill it for at least an hour before adding the chocolate shavings. Warm cream won't hold the shavings well and they'll just sink in or slide off.
Get the Full Details
The Part Everyone Gets Wrong
People tend to over-soak the sponge. The rule of thumb is about two to three tablespoons per layer, not a full cup. My first few attempts came out soggy because I was dousing the layers like I was making a trifle. The sponge should taste damp, not dripping. If you press your finger on it lightly, it should spring back. If it feels wet, you've gone too far. Another thing: the chocolate shavings. Use a vegetable peeler on a block of dark chocolate at least 70%. Pre-shredded chocolate from a bag won't stick properly and has a waxy texture that clashes with the cream. Just shave it yourself. It takes about two minutes. If your kitchen is warm, chill the mixing bowl and beaters in the freezer for ten minutes before whipping the cream. This is actually critical in summer. I used to skip this and wonder why the cream was always collapsing. It's not your technique. It's the temperature.
The cake is best made a day ahead. The flavors settle and the layers hold together much better. It'll keep in the fridge for three days, though the sponge does dry out slightly after the second day. If that happens, it still tastes fine but the texture isn't what it should be. Don't make this for a gathering where it'll sit out — it needs refrigeration from the moment it comes out of the oven until it goes into the mouth. Total active time is probably 40 minutes. The rest is waiting. Not bad for a proper showstopper.
