Preheat your oven to 425°F (220°C): Make sure your oven is perfectly preheated, as this will ensure consistent baking.
Grease 4-6 ramekins (or small cups): Use a bit of unsalted butter to grease the ramekins thoroughly, which will help in easily releasing the cakes once they’re done baking.
Melt the chocolate and butter together in a double boiler: Place the chopped dark chocolate and 1/2 cup of unsalted butter in a heat-proof bowl over a pot of simmering water. Stir until completely melted and smooth.
In a bowl, whisk the sugar, eggs, and vanilla together: In a separate bowl, combine 1 cup of granulated sugar, 4 large eggs, and 2 teaspoons of pure vanilla extract. Whisk until the mixture becomes light and fluffy, roughly 2-3 minutes.
Stir in the flour and salt until just combined: Gently fold in 1 3/4 cups of all-purpose flour and 1 teaspoon of salt. Be careful not to overmix, as this can create a tough texture.
Mix in the melted chocolate: Carefully fold the melted chocolate mixture into the batter until incorporated. This creamy mixture will create the rich flavor you’re aiming for.
Pour the batter into the prepared ramekins: Fill each ramekin about 3/4 full with the batter. Leave some space for the cakes to rise.
Bake for 12-15 minutes: Place the ramekins in the preheated oven and bake until the edges are firm but the centers are still slightly jiggly—about 12 to 15 minutes.
Cool for 1 minute, then invert onto plates: Let the cakes cool for about one minute, then carefully flip the ramekins onto serving plates. Tap gently to release the cake.