Heat oven to 350 degrees, place oven rack on lowest position.

Bring a small pot of water to a boil.

Chop the chocolates and set aside, separated.

Whisk the cocoa and water together in a large bowl.

Add the unsweetened chocolate and whisk until melted.

Whisk in the melted butter and oil.

Add the eggs, egg yolks, and vanilla.

Whisk in the sugar, then the salt and flour.

With a rubber spatula, fold in the chunks of bittersweet chocolate.

Scrape the batter into a 9x13 greased pan and bake for about 30 minutes, or until a toothpick comes out clean.

Let cool completely.