Steps

1. Measure 45g Unsalted Butter, 85g Chocolate Bar, and 90g Heavy Cream into a large bowl. Finely chop the chocolate bar and unsalted butter.
   🕒 00:44
2. Measure 30g Cake Flour and 40g Cocoa Powder into a separate bowl and mix well.
   🕒 01:03
3. Separate the eggs into yolks and whites. Be careful not to let any yolk get into the egg whites. This is crucial! The oil from the egg yolks can prevent the egg whites from whipping properly, so separate them carefully.
   🕒 01:14
4. Prepare the baking pan. Cut parchment paper slightly longer than the pan and double it up for the bottom to make it easier to remove.
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5. Sift the mixed Cake Flour and Cocoa Powder onto the parchment paper. This is a key step! Cocoa powder can be dusty, so sift it in an area with minimal surrounding items.
   🕒 01:46
6. Add 30g Granulated Sugar to the egg yolk bowl and mix until it becomes pale and thick immediately. This is important! If you don't mix right away, it will become lumpy.
   🕒 02:03
7. Heat the bowl with unsalted butter, chocolate bar, and heavy cream in the microwave in two stages. Be cautious! Chocolate can burn easily, so don't overheat all at once. Swirl the bowl midway to combine.
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8. After heating, even if the chocolate and butter aren't completely melted, stir thoroughly until smooth and glossy.
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9. Add the melted chocolate mixture to the egg yolk mixture and mix until the egg yolks are no longer visible.
   🕒 03:10
10. Preheat your oven to 170℃ (338℉).
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11. Add 80g Granulated Sugar all at once to the bowl of egg whites. Whip until you have a firm meringue where whisk marks remain. This is a vital step! Although the amount of sugar is high for the egg whites, it results in a stable meringue. Do not switch to a low speed; use it as is.
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12. Combine the chocolate and egg yolk mixture with the meringue. This is crucial! If the chocolate mixture is too cold, it will solidify and be difficult to mix. If it's cold, gently warm it in the microwave for a few seconds.
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13. Add half of the meringue to the chocolate mixture and fold until marbled.
    🕒 05:05
14. Add the sifted cake flour and cocoa powder. Fold from the bottom, rotating the bowl counter-clockwise, until just combined.
    🕒 05:13
15. Add the remaining meringue and fold gently, being careful not to deflate the air. The meringue in this recipe is strong, so it's resistant to deflating.
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16. Pour the batter into the prepared pan, mix to incorporate, and tap the pan firmly on the counter to remove air bubbles. This ensures even distribution of air throughout the batter, as the initial and final layers of batter may have different air content.
    🕒 06:09
17. Bake in the preheated 170℃ (338℉) oven for 25-30 minutes.
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18. Once baked, immediately tap the cake on the counter again and let it cool on a wire rack.
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19. Once cooled to room temperature, wrap it and let it rest in the refrigerator.
    🕒 07:02
20. Finish by dusting with non-melting powdered sugar. The surface cracking and slight dip in the center are signs of success for this moist and dense Gateau au Chocolat, which has a higher moisture content and less flour.
    🕒 07:54