In a large bowl, cream together the butter and the sugar. Add in the cocoa, vanilla, vegetable oil, and eggs and mix well. Stir in the flour, baking soda, and salt last. Mix until well combined and so no lumps remain.
Spread the batter into a greased 8x8 baking dish. Bake at 375 degrees for 15 to 20 minutes or until a toothpick inserted in the center of the brownies comes out clean. Let the brownies cool before cutting.
Optional topping for brownies include: powdered sugar, chocolate chips, powdered sugar + milk glaze, chocolate syrup, caramel, and butterscotch chips.