Preheat oven to 350°F. Line a 8x8-inch baking pan with parchment paper.
Add the chocolate and butter to a large heatproof bowl. Microwave in 30-second bursts, stirring in between, until the mixture is melted and smooth. Whisk in the granulated sugar. Add the eggs, vanilla extract and Guinness and whisk until well combined. Stir in the flour and salt until the batter is uniform (I had to use an electric mixer to get rid of the lumps). Pour the batter into the pan.
Bake for about 25 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs attached. Transfer the pan to a wire rack and cool the brownies completely in the pan.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.