Preparation Steps

• Preheat the oven to 350°F (175°C). Grease an 8-inch round cake pan and line the bottom with parchment paper.
• In a heatproof bowl set over simmering water, melt the butter and chopped semisweet chocolate, stirring until smooth. Remove from heat and let cool slightly.
• Whisk together the eggs and granulated sugar until pale and slightly thickened. Stir in the vanilla extract.
• Gradually pour the melted chocolate mixture into the egg-sugar mixture, stirring continuously to combine.
• Sift together the flour, cocoa powder, salt, and baking powder. Gently fold the dry ingredients into the wet ingredients until just combined; do not overmix.
• Pour the batter into the prepared pan and smooth the top. Sprinkle chocolate chips evenly over the batter, if using.
• Bake for 30 to 35 minutes, or until the center is set and a toothpick inserted near the center comes out with a few moist crumbs. The top should have a crackly crust.
• Allow the cake to cool in the pan on a wire rack for 15 minutes, then invert onto the rack to cool completely. Slice and serve.