Ultimate Chocolate Custard Lava Cake with Glossy Ganache

Servings: 12-16 generous slices
Prep Time: 1 hour 30 minutes (plus cooling/chilling)
Bake Time: 28-35 minutes
Chill Time: At least 4 hours (best overnight)
Total Time: About 6-7 hours (mostly hands-off)

Why This Cake Will Become Your Signature Dessert

This isn’t just any chocolate cake. The sponge uses oil + buttermilk for unbeatable moisture that lasts 4-5 days. The filling is classic French pastry cream (crème pâtissière) — thick, luxurious, and stable enough to hold shape when sliced, yet soft enough to flow like molten lava when you cut in. The ganache gives that professional bakery mirror finish and seals in freshness. It’s the perfect balance between rich indulgence and elegant sophistication.

Ingredients

Chocolate Cake Layers (makes three 20-23 cm layers)

280 g (2¼ cups) all-purpose flour
75 g (¾ cup) unsweetened Dutch-process cocoa powder (for deeper color & flavor)
2 tsp baking soda
1 tsp baking powder
1 tsp fine salt
400 g (2 cups) granulated sugar
2 large eggs + 1 large yolk (room temperature)
180 ml (¾ cup) neutral oil (sunflower, canola, or light olive)
240 ml (1 cup) buttermilk (room temperature)
240 ml (1 cup) very hot coffee or water (instant coffee dissolved works great)
1 tbsp pure vanilla extract
1 tsp white vinegar (activates the leavening for extra lift)

Vanilla Pastry Cream Filling (thick & stable version – makes ~800-900 g)

500 ml (2 cups + 1 tbsp) whole milk
120 ml (½ cup) heavy cream (35% fat)
1 large vanilla bean (split & scraped) OR 2½ tsp pure vanilla bean paste OR 3 tsp vanilla extract
120 g (½ cup + 1½ tbsp) granulated sugar (divided)
6 large egg yolks (save whites for another use)
45 g (⅓ cup) cornstarch
45 g (3 tbsp) unsalted butter, very soft, cut into cubes
Pinch of salt

Shiny Chocolate Ganache Coating

340 g (12 oz) good-quality dark chocolate (54-65% cocoa) – chopped or callets
340 ml (1⅓ cups + 1 tbsp) heavy cream (35% fat)
2 tbsp glucose/corn syrup or honey (optional – for extra shine & flexibility)
45 g (3 tbsp) unsalted butter, softened (for silkier finish)
Pinch of fine salt

Step-by-Step Instructions

1. Prepare the Chocolate Cake Layers

Preheat oven to 170°C (340°F) conventional / 150°C (300°F) fan. Grease three 20-23 cm round cake pans, line bottoms with parchment, grease again, dust lightly with cocoa.

In a very large bowl, sift together flour, cocoa, baking soda, baking powder, and salt. Whisk in sugar thoroughly — this prevents lumps.

In a separate jug, whisk eggs + yolk, oil, buttermilk, vanilla, and vinegar until completely uniform.

Make a well in dry ingredients. Pour wet mixture in. Start mixing gently with a whisk, then pour in the hot coffee/water in 3 additions while whisking continuously. The batter will be very thin — that’s normal! It creates steam during baking for ultra-moist texture.

Divide batter equally between pans (about 550-600 g each). Tap pans firmly on counter to release air bubbles.

Bake 28-35 minutes (rotate halfway). Toothpick should come out with moist crumbs — not wet batter. Cool in pans 15 minutes, then turn out onto rack. Cool completely (wrap & chill if making ahead).

Pro tip: Level the tops with a serrated knife while slightly warm for perfectly flat layers.

2. Make the Vanilla Pastry Cream (Do this while cakes bake/cool)

In a medium saucepan, heat milk + heavy cream + vanilla bean (pod & seeds) over medium heat until steaming and small bubbles appear around edges (do not boil). Remove from heat, cover, let infuse 20-30 minutes.

In a large heatproof bowl, whisk egg yolks, half the sugar (60 g), cornstarch, and salt until very smooth and pale (2-3 minutes).

Slowly pour about ⅓ of hot milk mixture into yolk mixture while whisking constantly (tempering — prevents scrambled eggs). Pour everything back into saucepan.

Cook over medium heat, whisking constantly. It will look thin → lumpy → suddenly thick like pudding (about 4-7 minutes). Once large bubbles burst on surface, cook 1 more full minute to fully activate cornstarch.

Remove from heat. Whisk in butter cubes until completely melted & smooth. Strain through fine sieve into clean bowl (removes any lumps or cooked egg bits).

Press plastic wrap directly on surface (prevents skin). Cool to room temperature, then refrigerate at least 3 hours (best overnight). It will thicken dramatically.

3. Assemble the Cake

Level all cake layers if needed. Place first layer on cake board/plate. Pipe or spread a thin dam of stiff buttercream/ganache around edge (prevents filling leaking).

Spread or pipe about ⅓ to ½ of chilled pastry cream generously in center (leave dam clear). Top with second layer, repeat. Add final layer.

Refrigerate cake 30-60 minutes (sets filling, firms structure).

4. Make & Apply the Shiny Ganache

Place chopped chocolate + salt in heatproof bowl.

Heat cream (and glucose if using) until just simmering. Pour over chocolate. Wait 1 minute. Stir slowly from center outward until glossy & smooth. Add soft butter, stir until incorporated.

Cool ganache to 30-32°C (86-90°F) — warm enough to pour but thick enough not to run off completely.

Pour ganache over chilled cake center, let it flow naturally over edges for drip effect. Use offset spatula to smooth top & encourage drips.

For ultra-shiny finish: refrigerate 10 minutes, then gently polish top with warm offset spatula.

Chill cake 2-4 hours minimum (best overnight) before slicing — allows ganache to set while filling stays soft.

Serving & Storage Tips

Serve slightly chilled or at cool room temperature — the pastry cream flows beautifully when cut.

Store covered in refrigerator up to 5 days. Bring to room temp 30-45 minutes before serving for best texture.

Freezes well (whole or slices) up to 2 months — thaw overnight in fridge.

Variations & Troubleshooting

Want even more lava effect? Make extra pastry cream and warm slightly before serving slices.
Alcohol twist: Add 2-3 tbsp Baileys/Kahlua to pastry cream.
Too runny ganache? Use more chocolate next time or cool longer.
Cake dry? You likely overbaked — trust moist crumbs test.
Gluten-free? Use 1:1 GF flour blend + ½ tsp xanthan gum.

This cake combines the best elements of classic chocolate indulgence with French pastry elegance. Make it once, and you’ll be asked to bring it to every celebration. Enjoy every decadent bite! 🍫✨