Preheat over to 350 degrees
Bring stout and butter to simmer in a large saucepan, stirring often. DO NOT boil it.
Add unsweetened chocolate chips to hot stout/butter mixture. Whisk until chocolate is melted and combined.
Add sugar to chocolate mixture and whisk to combine until melted/combined.
Place mixture into a stand mixer or a bowl if using a hand mixer. Add whisk attachment.
In a separate bowl, sift together flour, baking soda, and salt.
In your mixer/bowl, mix eggs and sour cream on medium speed until combined.
Add the chocolate/stout mixture on medium/low speed until combined.
Slowly add the flour mixture until all combined, making sure to scrape and incorporate from the sides.
Place in your cupcake holders and fill to about 2/3 full.