Preheat the oven to 350°F and grease an 8 inch round cake pan.

Heat the stout and butter in a saucepan over medium heat until the butter melts, then whisk in the cocoa powder until smooth, and set aside to cool for 10 minutes.

Whisk the flour, sugar, baking soda, and salt together in a bowl.

Whisk the sour cream, eggs, and vanilla together in another bowl, then whisk in the cooled stout mixture.

Pour the wet mixture into the dry ingredients and whisk until smooth, then pour into the prepared pan.

Bake for 30 to 35 minutes, until a toothpick inserted in the center comes out clean.

Cool the cake completely in the pan, at least 1 hour, then crumble it into a large bowl with your hands, no large chunks should remain.

Heat the heavy cream until it just starts to steam, pour it over 4 ounces of the chopped chocolate, and let sit for 2 minutes before stirring until smooth.

Pour the warm ganache over the crumbled cake and mix with a spatula until it holds together when pressed.

Roll the mixture into 24 balls, about 1 tablespoon each, set them on a parchment lined tray, then chill for 30 minutes, until firm.

Melt the remaining 8 ounces of chocolate in short bursts in the microwave, stirring between each, until smooth.

Dip each ball in the melted chocolate using a fork, letting the excess drip off, and set back on the parchment to harden for about 20 minutes before serving.