Preheat the oven to 375 degrees F. Spray a 9-inch cake pan with non-stick cooking spray. Then add a piece of parchment paper to the bottom, spray again with non-stick cooking spray, set aside.
In a large microwave-safe bowl add the chopped chocolate and butter. Microwave in 20-second intervals, stirring between each interval until fully melted.
Next, whisk in the sugar until combined.
Add the eggs one at a time making sure to whisk in fully before adding the next one.
Whisk in the vanilla then the cocoa powder until smooth.
Pour the batter into the prepared cake pan and smooth out the top with a spatula.
Bake for 26-30 minutes until a toothpick inserted into the center comes out mostly clean.
Remove the cake from the oven and let the cake cool in the pan for 10 minutes, remove from the pan and discard the parchment paper. Place on a wire rack over a sheet pan to cool completely.
Once the cake has cooled, make the ganache. Add the chopped chocolate to a heat-proof bowl and set aside.
Place the heavy cream in a microwave-safe bowl or measuring cup and heat in 30-second intervals until it reaches 180-190°F.
Pour the hot cream over the chopped chocolate and let it sit for about 5 minutes.
Add the vanilla and whisk everything together until smooth.
Pour the ganache over the top of the cake making sure that the sheet pan catches any drips. Using an offset spatula, smooth the ganache over the top of the cake.
Let the cake sit for 1-2 hours until the ganache is set. Top with desired your toppings and serve immediately.