01 -
Put your oven to 180°C (350°F) and place the rack in the middle. Coat an 8- or 9-inch springform pan with butter, then dust with flour or cocoa powder. Leave it aside for later.
02 -
Place the chocolate chunks and butter in a medium heatproof bowl. Put the bowl over a water bath (bain-marie) and melt them together. Let it sit for about 10-15 minutes to cool down.
03 -
Grab a big bowl and beat the yolks with 100g sugar until light and fluffy. Slowly pour in the cooled chocolate and butter mixture while whisking. Sprinkle in cornstarch and gently mix till smooth.
04 -
In a fresh big bowl, whip the egg whites with the salt until you get stiff peaks. Add the rest of the sugar (100g) little by little as you mix. Using a spatula, gently blend a small batch (about a quarter) of the whipped whites into the chocolate batter. Carefully fold in the rest, a bit at a time, until the mix is airy and soft.
05 -
Pour the fluffy batter into your greased pan. Bake for around 25-30 minutes. The top should puff up, edges firm, but the center should jiggle slightly. Place the pan on a cooling rack. The cake might collapse and get crinkly as it cools. Let it cool for 15 minutes minimum before you take it out of the pan.
06 -
Serve it warm if you like it gooey, let it hit room temperature for a softer bite, or chill it if you prefer it denser.