For the cake:
Cooking spray
2 sticks (1 cup) unsalted butter
1 cup Guinness stout
3/4 cup extra-dark unsweetened cocoa powder
2 large eggs
1 cup sour cream
1 tablespoon vanilla extract
2 cups all-purpose flour
1 cup granulated sugar
1 cup packed light brown sugar
1 1/2 teaspoons baking soda
3/4 teaspoon salt

For the frosting:
1 stick (1/2 cup) unsalted butter, at room temperature
4 ounces cream cheese, at room temperature
2 cups powdered sugar, divided

Equipment:
Parchment paper (optional)
Measuring cups and spoons
Mixing bowls
Small saucepan
9-inch cake pan that is 3 inches deep
Whisk
Electric hand or stand mixer
Wire cooling rack