Preheat your oven to 350°F. Grease an 8x8 baking pan and lining with parchment paper, if desired, and set aside.
In a large bowl, mix the flour, cocoa powder, sugar, and salt together until combined.
In a separate bowl, whisk together the melted butter, vegetable oil, eggs, and vanilla extract until combined.
Add the wet ingredient mixture into the dry mixture and whisk together until just combined.
Pour the brownie batter into the prepared pan and spread it out evenly. Pop into the preheated oven and bake for 32-35 minutes. Once out of the oven, allow the brownies to cool completely.
Making the Ganache
Heat the heavy cream in a microwave safe bowl or cup for about a minute until very warm. Add in the chopped chocolate bar. Let sit for about 2 minutes.
Using a fork or a small whisk, mix the heavy cream and melted chocolate together until combined and the ganache is thick and smooth.
Assembling the Brownies
Pour the ganache onto the cooled brownies and spread into an even layer. Pop the brownies into the refrigerator for 30 minutes to an hour, or until the ganache is set.