Preheat oven to 350°F (175°C).

Grease and flour a 12 x 18-inch cookie sheet.

In a bowl, mix together flour and sugar.

Set aside the flour and sugar mixture.

In a saucepan, mix margarine, oil, cocoa, and water.

Heat the saucepan mixture until it comes to a boil.

Pour the boiling mixture over the sugar and flour mixture.

Beat the combined mixture until well incorporated.

Add buttermilk, eggs, soda, and vanilla to the batter.

Beat again until smooth.

Pour the batter into the prepared cookie sheet.

Bake for 20 minutes, or until a toothpick inserted into the center comes out clean.

Let cool slightly.

Frost with chocolate frosting (optional).

Sprinkle with nutmeats (optional).