Start by preheating your oven to 350°F (175°C). For easy removal later, grease your 9-inch round cake pan or line it with parchment paper.

Combine the dark chocolate and butter in a microwave-safe bowl. Warm the mixture in 20-second intervals, stirring each time, until it becomes completely melted and smooth. If you prefer the double boiler method, place the bowl over simmering water and stir occasionally until the mixture melts. Be sure to watch the chocolate carefully to prevent burning.

Once melted, allow the mixture to cool slightly for a few minutes.

In a separate bowl, whisk the eggs and sugar together until they form a smooth, light mixture. This creates a nice texture for the final cake.

Slowly pour the melted chocolate-butter mixture into the egg-sugar blend, mixing gently until the ingredients are well combined and smooth.

If you're using flour, sift it along with a pinch of salt into the mixing bowl. Stir the mixture just until everything is combined. Take care not to overmix, as it could impact the texture of the cake.

Transfer the batter into the prepared pan, smoothing it out evenly. Bake it in the preheated oven for 25 to 30 minutes, or until the cake is firm on the edges with a slightly soft center. As the cake cools, it will firm up, so don’t be concerned if there’s a small dip in the center.

Once the cake is done baking, remove it from the oven and let it sit in the pan for approximately 10 minutes. Then, gently transfer it to a wire rack to cool completely. The cake will firm up as it cools, achieving the perfect texture.

Once cooled, decorate your cake with toppings of your choice. A drizzle of chocolate ganache, a dusting of powdered sugar, or fresh berries are all great options to elevate the flavor and presentation.

Once the cake has cooled and been topped, slice it into generous pieces and enjoy your indulgent chocolate decadence!