Ingredients :

• 70% Dark Chocolate — This is the main ingredient, so don’t skimp on it. A 52% cocoa chocolate will give you a result that’s too sweet and a bit flat. Aim for at least 70% — Lindt Excellence, Valrhona Caraïbe, or even a store brand if the percentage is right. Take a whole 200g bar, not the small bags of chocolate chips.
• Unsalted Butter — 100g, cut into cubes. Use unsalted butter here, not semi-salted, because you want to control the salt yourself. It must melt with the chocolate, so the softer it is at the start, the less you risk overheating the chocolate while waiting for it.
• Eggs — 4 eggs, and you’re going to separate them. The yolks go into the melted chocolate, the whites will be whipped. This is the only technical step of the recipe, and it’s what gives the cake its paradoxical lightness despite all that richness. Eggs at room temperature — whites whip better and faster.