Preheat the oven to 350 degrees Fahrenheit and line a 9X9 baking dish with parchment paper and make sure that the paper over hangs the pan for easy removal of the brownies.

In a large mixing bowl, stir together the vegetable oil, Guinness, sugar and vanilla extract.

Add in the butter and eggs. Mix until well combined.

In a separate bowl, stir together the flour and cocoa powder until well combined.

Slowly add the dry ingredients into the butter/oil mixture until just combined.

Pour the batter into the prepared pan into an even layer.  Bake for 35-38 minutes until a toothpick inserted into the center of the brownies comes out clean.

Let the brownies cool completely at room temperature before topping them with the frosting.

Beat the butter in a large mixing bowl of a stand up mixer with a paddle attachment until light and fluffy (approximately 1 minute).

Slowly add in the powdered sugar and mix on low speed until combined.

Add in the vanilla extract and 2 tablespoons of the Guinness beer.  Continue to mix until the frosting is smooth and fluffy (3-4 minutes).  Then check the frosting consistency and gradually add in the last tablespoon of Guinness until the frosting is the consistency you prefer.

Spread the frosting over the cooled brownies.

Carefully remove the brownies from the pan by lifting them up with the parchment paper.  Slice the brownies into squares and then they are ready to serve and enjoy!