Preheat the oven to 200°C.
Grease 4 ramekins with butter and dust with cocoa powder.
In a microwave-safe bowl, melt 200 grams of dark chocolate and 100 grams of unsalted butter together. Stir until smooth and let it cool for a few minutes.
In a separate bowl, whisk together 2 large eggs, 2 egg yolks, and 100 grams of powdered sugar until the mixture is pale and fluffy.
Gently fold the cooled chocolate mixture into the egg mixture.
Sift 50 grams of all-purpose flour into the mixture and fold gently until well combined.
Divide the batter evenly among the prepared ramekins.
Place the ramekins on a baking tray and bake for 10-12 minutes, or until the edges are set but the center is still slightly jiggly.
Carefully remove the ramekins from the oven and let them cool for 1-2 minutes.
Run a knife around the edges of the ramekins to loosen the choco lava cakes, then invert them onto serving plates.