Preheat oven to 350 F / 175 C and lightly grease an 8 x 8 inch baking pan, and then line it with parchment paper.
In a medium sized bowl, combine together the melted butter, oil and sugar. Using an electric handheld beater, beat for about a minute.
Add the eggs and vanilla, and beat for another minute until the mixture is fluffy about 1-2 minutes.
Now add in the dry ingredients to the bowl: flour, cocoa powder and salt. Gently fold by hand, the dry ingredients into the wet ingredients until JUST combined. Do not over mix.
Fold in the chocolate chunks, and then pour the batter into the baking pan.
Bake for 25 minutes or until the middle of the brownies no longer jiggles. Be careful not to over bake, as the brownies will continue cooking in the hot pan once removed from the oven.
Remove from oven, and allow to cool completely before cutting the brownies. For the pictures I sliced the brownies into 9 pieces, but if you want you can slice them into 16 pieces.