Chocolate Layer Cake

Name: Chocolate Layer Cake
Prep time: 45 min
Cook time: 2 h 45 min
Total time: 3 h 30 min
Ingredients: 250 g (2 cups) all-purpose flour; 300 g (1½ cups) sugar; 75 g (¾ cup + 1 tbsp) cocoa powder, Dutch-processed or natural; 8 g (1½ tsp) baking soda; 5 g (1 tsp) baking powder; 5 g (¾ tsp) fine sea salt; 2 large eggs (about 100 g without shells), at room temperature; 240 g (1 cup) buttermilk, at room temperature; 120 ml (½ cup) neutral oil; 10 ml (2 tsp) vanilla extract; 240 ml (1 cup) hot strong coffee or hot water; 300 g (10½ oz) dark chocolate (55–70%), finely chopped; 450 ml (1¾ cups + 2 tbsp) heavy (double) cream, 35–40% fat; 30 g (1½ tbsp) golden syrup or honey; 1 pinch fine sea salt

Dark, moist sponge with a glossy whipped ganache frosting

Makes: 1 two-layer cake (20 cm / 8 in)
Hands-on: 45 min
Total: 3 h 30 min
Level: Some skill

The birthday cake. Cocoa bloomed in hot coffee gives a deep, dark crumb that stays moist for days, and the frosting is simply chocolate and cream, whipped to a silky spread. Two layers, no special skills.

Ingredients

Cake

250 gall-purpose flour (2 cups)
300 gsugar (1½ cups)
75 gcocoa powder (¾ cup + 1 tbsp)Dutch-processed or natural
8 gbaking soda (1½ tsp)
5 gbaking powder (1 tsp)
5 gfine sea salt (¾ tsp)
2large eggs (about 100 g without shells)at room temperature
240 gbuttermilk (1 cup)at room temperature
120 mlneutral oil (½ cup)
10 mlvanilla extract (2 tsp)
240 mlhot strong coffee or hot water (1 cup)

Whipped ganache

300 gdark chocolate (55–70%), finely chopped (10½ oz)
450 mlheavy (double) cream, 35–40% fat (1¾ cups + 2 tbsp)
30 ggolden syrup or honey (1½ tbsp)
1 pinchfine sea salt

Diet: Vegetarian
Allergens: gluten, egg, milk

Method

Ganache first, as it needs time to cool: bring the cream and syrup just to a simmer, pour over the chocolate in a bowl, add the salt, wait 2 minutes, then stir from the center until smooth and glossy.
Cover the surface and leave at cool room temperature 2–3 hours, or chill about 1 hour, until it's cold and as thick as pudding but not set hard. 2 h
Heat the oven to 175°C (350°F). Grease two 20 cm (8 in) round pans, at least 5 cm deep, and line the bases with baking paper.
In a large bowl, whisk the flour, sugar, cocoa, baking soda, baking powder and salt, breaking up any cocoa lumps.
Add the eggs, buttermilk, oil and vanilla and whisk until smooth. Pour in the hot coffee slowly, whisking, to a thin, glossy batter. It will be very runny; that is correct.
Divide between the pans and bake 30–35 minutes, until the tops spring back and a skewer comes out clean. Cool in the pans 15 minutes, then turn out onto a rack and cool completely, about 1 hour. 1 h 20 min
Whip the cooled ganache with an electric mixer (or a balloon whisk) on medium for 1–2 minutes, just until it lightens in color and holds soft peaks. Stop there; overwhipped ganache turns grainy. 2 min
Set one layer on a plate and spread with a third of the ganache. Top with the second layer and cover the top and sides with the rest, swirling with the back of a spoon.

Why it works

Hot liquid dissolves the cocoa and releases its flavor compounds, a step called blooming, and coffee deepens the chocolate without tasting of coffee. Oil keeps the crumb moist and soft even when cold, and the thin, high-liquid batter bakes into a very tender cake. Ganache is an emulsion of cocoa butter and cream fat; whipped when cold, it traps air like whipped cream and sets into a light, stable frosting.

Common mistakes

Whipping the ganache while still warm (it won't thicken) or too long (it seizes and turns grainy). If grainy, melt a quarter of it, then whisk it back in.
Shallow pans, which overflow with this runny batter. Use pans at least 5 cm deep.
Frosting warm layers, which melts the ganache.

Variations

Sheet cake: Bake in a 23 × 33 cm (9 × 13 in) pan for 35–40 minutes and spread with half the ganache, unwhipped and just warm, as a glaze.
Cupcakes: Fill 24 lined cupcake cups two-thirds full and bake 18–20 minutes.

Make ahead and storage

Layers keep 2 days wrapped at room temperature, or freeze for 2 months. The frosted cake keeps 2 days in a cool spot under a cake dome, or 4 days in the fridge (bring it back to room temperature for 1 hour before serving).

Notes

Fan oven: 155°C (310°F). No buttermilk: stir 10 ml lemon juice into 230 ml milk and rest 5 minutes. Many dark chocolates contain soy lecithin; check the label if cooking for someone with a soy allergy.