In a large mixing bowl, sift together the all-purpose flour, cocoa powder, baking powder, baking soda, salt, and granulated sugar until well combined.

Mixing Wet Ingredients

Melt Butter

In a saucepan over medium heat, melt the unsalted butter. Once melted, remove from heat and let cool slightly.

Combine Wet Ingredients

In another mixing bowl, whisk together the stout beer, melted butter, eggs, vanilla extract, and sour cream until smooth.

Baking

Combine Mixtures

Pour the wet ingredients into the dry ingredients. Mix until just combined, being careful not to overmix.

Bake the Cake

Pour the batter into the prepared baking pan and bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean.

Cool the Cake

Remove the cake from the oven and let it cool in the pan for 10 minutes. Then transfer to a wire rack to cool completely.

Serving

Prepare Optional Topping

If desired, dust with powdered sugar or drizzle with chocolate ganache before serving.

Serve and Enjoy

Slice the cake and serve it to your guests. Enjoy your rich chocolate stout cake!