Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round cake pan, or line it with parchment paper.

1. In a medium saucepan, melt the butter and 1 cup of chocolate chips together over medium heat, stirring occasionally until smooth. Remove from heat and let it cool slightly.
2. Whisk in the granulated sugar and brown sugar until fully combined.
3. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.
4. In a separate bowl, sift together the flour, cocoa powder, baking powder, and salt.
5. Gradually fold the dry ingredients into the wet ingredients until just combined. If using, fold in the additional chocolate chips.
6. Pour the batter into the prepared cake pan, spreading it out evenly.
7. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs (but not wet batter). The top should appear set, and the edges should be pulling away slightly from the pan.
8. Let the cake cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.
9. Once cooled, serve the cake as is or with your choice of toppings, such as whipped cream, chocolate ganache, or fresh berries.