Add a 14 ounce stout beer into a saucepan and bring to a simmer over medium high heat
Once simmering, reduce the heat to medium and simmer until the beer is reduced to 1/2 cup in volume (about 15 minutes)
While the beer is reducing, preheat your oven to 350 degrees and grease a 9” round cake pan or 11”x7” baking dish and line with parchment paper
Whisk 1 cup of all purpose flour with 1/2 cup of dark dutch cocoa powder, 1 teaspoon of baking powder, 1 teaspoon of baking soda and 1 teaspoon of salt in a large bowl
In a separate bowl, whisk 3/4 cup of granulated sugar, 1/4 cup of brown sugar, 3/4 cup of vegetable oil, 2 large eggs and a teaspoon of vanilla extract until fully combined
Add the wet ingredients to the dry ingredients and mix until just combined
Add the 1/2 cup of reduced stout beer and mix until evenly distributed
Transfer the batter into the prepared cake pan