Preheat oven to 350. Line 48 muffin cups with foil cup thingies. (The original recipe says to make 30, but that's way too big. You want the cupcake to be somewhat below the level of the liners so that you have room for the glaze.) Give each one a quick spray with Pam. That makes it much easier for people to get the foil off when they're eating them.

Put the butter and stout in a large mixing bowl and heat in the microwave on 50% power for 3-4 minutes, or until the butter is melted. The power of your microwave and the softness of the butter will all affect the time. Whisk in the cocoa until smooth and cool the mixture to room temperature. Combine the flour, sugar, baking powder, and salt in a small bowl, and the eggs and sour cream is yet another small bowl. Then use a mixer to beat the egg mixture into the cocoa mixture, then add the flour mixture and beat that in at low speed, scrape down the sides of the bowl and then beat for one minute. Scoop the batter into the muffin tins, filling the cups about 1/3 full. You can bake them in batches if your oven doesn't do a good job with multiple pans. I have a convection oven and still do the switching-around business halfway through baking. Since these are so small I've shortened the baking time to 10-12 minutes, but be sure to test them with a toothpick to make sure they're done--the toothpick needs to come out clean. Cool for 5 minutes in the pans and then turn them out onto a rack and cool completely before frosting.