Start by heating your oven to 425°F (220°C). While it warms up, butter the inside of 4 ramekins really well so nothing sticks. Lightly dust them with cocoa powder or a little flour, tapping out the extra. Set the ramekins on a baking sheet and place aside.

Place the chocolate and butter in a heatproof bowl. Set the bowl over a pot of gently simmering water (make sure the bottom of the bowl doesn’t touch the water). Stir slowly until everything is melted and smooth. Remove from the heat and stir in the heavy cream. Let the mixture cool for a couple of minutes.

In another bowl, whisk together the 2 whole eggs, 2 egg yolks, and both portions of sugar. Keep whisking until the mixture becomes pale, slightly thick, and creamy. This should take about 2–3 minutes.

Slowly pour the melted chocolate mixture into the egg mixture, whisking gently as you go. Add the vanilla extract and salt. Sift in the flour and black cocoa powder. Using a spatula, fold everything together carefully until just combined. Don’t over mix stop as soon as the batter looks smooth.

Pour the batter evenly into the prepared ramekins, filling each about three quarters full. Bake for 12–14 minutes. The edges should look firm, while the center should still be soft and slightly jiggly when you gently shake the pan.

Allow the cakes to sit for 1–2 minutes after removing them from the oven. Carefully run a knife around the edges if needed, then turn each one out onto a plate. Finish with a dusting of powdered sugar or serve warm with a scoop of vanilla ice cream.