Preheat oven to 350°F. Line an 8 inch square pan with parchment paper or spray with nonstick cooking spray.
In a medium sized bowl whisk the butter, oil, and sugar for 1 minute. Add the eggs and vanilla and mix vigorously for 1 minute or until slightly paler in color.
Sift the flour, cocoa, and salt into the wet ingredients. Using a rubber spatula fold the dry ingredients into the wet mixture until just combined.
Pour batter into the prepared pan and bake for 18-20 minutes. Bake until the middle no longer jiggles. The tops will be just set, and will continue to bake in the pan as it cools. If you insert a toothpick into the center the toothpick should come out with some fudgy crumbs. This will provide a very fudgy type brownie.