Preheat the oven to (176 c) 350 degrees. Prepare an 8x8 inch baking pan with a parchment overhang and coat with baking spray.
In a medium-sized bowl, combine melted butter, granulated sugar, and brown sugar. Use a hand mixer on medium speed to mix them together.
Add the eggs one at a time, mixing well after each addition. Mix in the oil and vanilla extract.
In a separate bowl, combine the flour, cocoa powder, and salt. Sift the ingredients together to remove lumps.
Reduce the speed of the mixer and gradually add the flour mixture to the wet mixture, mixing until all ingredients are combined.
Pour the brownie batter into your prepared baking pan. Sprinkle chocolate chunks on the top.
Bake for approximately 30 minutes, or until a toothpick inserted into the center comes out slightly clean. Avoid overbaking.
Remove the brownies from the oven and allow them to cool on a cooling rack.
Once cooled, cut the brownies into pieces and serve.
