Steps
1. Preheat your oven to 175°C and grease a small cake pan or line with parchment paper.
2. In a bowl, sift together flour, cocoa powder, baking powder, salt, and sugar.
3. In another bowl, beat the egg, then whisk in milk, oil, and vanilla extract.
4. Gradually add the dry ingredients into the wet mixture, stirring gently until just combined. Avoid overmixing.
5. Fold in the chopped dark chocolate if using.
6. Pour the batter into the prepared pan and smooth the top.
7. Bake for 20-25 minutes or until a toothpick inserted in the center comes out clean.
8. Let the cake cool slightly before removing from the pan. Serve warm or at room temperature.