Ingredients

   
100g dark chocolate (60–70% cacao), chopped
42g unsalted butter, cubed
12g Dutch-process cocoa powder
100g whole milk (2% also works)
3 large eggs (50g without shell), yolks and whites separated
1 extra egg yolk (~18g)
38g sugar (for egg yolks)
20g cake flour
1g kosher salt
38g sugar (for egg whites)
  Confectioners’ sugar or cocoa powder for dusting (optional)

Steps

  1. Preheat oven to 350°F. Line a 15cm round cake pan with parchment paper.

  2. Melt dark chocolate and butter in a double boiler (bowl over simmering water, not touching). Stir until smooth. Remove from heat — keep water and steam out of the mixture.

  3. Add cocoa powder and stir until no lumps remain. Gradually stir in milk until smooth.

  4. Refrigerate or freeze egg whites for 15 minutes until cold.

  5. In a large bowl, whisk the 3 egg yolks plus the extra yolk and 38g sugar vigorously until creamy and pale. Add the chocolate mixture and mix well.

  6. Sift 20g cake flour into the batter. Gently whisk until just incorporated — do not overmix. Add salt and stir.

  7. Whip cold egg whites on medium-low until bubbly and foamy. Gradually add 38g sugar while beating. Increase to high speed and beat until stiff, glossy peaks (about 2 minutes).

  8. Fold one-third of the meringue into the batter and mix well. Fold in another third gently. Add the last third and fold until just combined — don’t deflate the bubbles.

  9. Pour batter into the prepared pan and smooth the surface.

  10. Bake at 350°F for 15 minutes, then reduce to 325°F and bake 20 more minutes. The center will still wobble slightly — this is correct. Do not skewer-test this cake.

  11. Cool completely in the pan on a wire rack, about 4 hours. Can also refrigerate overnight.

  12. Dust with confectioners’ sugar or cocoa powder. Microwave chilled slices for 5 seconds for a melt-in-your-mouth texture.

Analysis

Total batter weight: 519g

Component Amount %
Structure solids (flour + cocoa + cocoa solids) 61g 11.8%
Fat (chocolate, butter, egg) 100g 19.3%
Sugar (added + chocolate) 105g 20.2%
Liquid (milk, egg water) 220g 42.4%
Egg/protein 33g 6.4%

A flourless-leaning, meringue-lightened chocolate cake, tuned moister than its matcha sibling’s dark counterpart would otherwise run: structure is low (~12%, mostly the chocolate’s cocoa solids — only 20g flour, with the cocoa trimmed to 12g so fewer thirsty solids draw water from the crumb) and egg is high (6.4% protein, with whipped whites doing the lift), which is why the interior stays molten and fudgy rather than crumbed like a butter cake. Liquid is high (~42%) — milk bumped to 100g and an extra yolk added — because the chocolate and cocoa butter set it as they cool; the extra yolk enriches and emulsifies without adding flour-type structure. Flour is deliberately left at 20g: it is the binder that lets the cake unmold, and cutting it would make the cake more fragile, not moister.

Notes

  • Tuned moister than a plain cocoa swap of the matcha recipe. Cocoa powder is drying — its non-fat solids (mostly fiber, some protein/starch) soak up nearly their own weight in liquid — and dark chocolate adds cocoa solids that white chocolate doesn’t, so a like-for-like swap of the matcha version bakes drier and firmer. Three levers pull it back: milk raised to 100g, cocoa trimmed to 12g (fewer thirsty solids), and an extra egg yolk for fat + emulsification. Flour stays at 20g on purpose — it’s the binder, not a moisture lever.
  • Prefer more chocolate punch over softness? Take the cocoa back up toward 18–25g; add ~7g milk per extra 7g cocoa to keep it hydrated (cocoa absorbs up to ~100% of its weight in water). Or use a higher-fat cocoa (20–24%) — fudgier and less absorbent than standard 10–12% cocoa.
  • Want to use butter instead of the extra yolk? You can, but butter is a weak moisture lever — it firms as it cools and reads drier. Better moisture fats are the extra yolk (used here), a little neutral oil in place of some butter (oil stays liquid), or swapping part of the sugar for brown sugar/honey as a humectant.
  • To intensify chocolate flavor without affecting texture, add 1–2g espresso powder to the batter with the cocoa. It deepens chocolate notes without tasting like coffee.
  • Use Dutch-process cocoa for a smoother, less acidic flavor. Note that Dutch-process absorbs even more liquid than natural cocoa.
  • Use good quality dark chocolate (60–70% cacao), not chocolate chips — chips have stabilizers that affect melting.
  • The inside is intentionally soft and fudgy — don’t overbake.
  • Requires 4 hours cooling time before cutting.
  • Optional ganache topping: heat 80g heavy cream to a simmer, pour over 80g chopped dark chocolate, let sit 1 minute, stir until smooth, add 14g butter. Cool until pourable, then pour over the unmolded cake.
  • Cake flour is required. Homemade: for every 120g AP flour, remove 16g and replace with 16g cornstarch, sifted 3–4 times.
  • Double the recipe for a 20–23cm pan, triple for 25–28cm.
  • Store refrigerated 3 days or frozen 1 month.