Mix wet ingredients
In a large bowl, combine Guinness, milk, vegetable oil, and vanilla. Beat in 3 eggs, one at a time. Mix in sour cream.
Mix dry ingredients
In another bowl, whisk together the cocoa, sugar, flour, and baking soda.
Finish the batter
Gradually add the dry ingredients to the Guinness mixture. Portion the batter into lined cupcake tins and bake.
Frost the cupcakes
After cooling completely, frost the cupcakes with vanilla buttercream and top with chocolate jimmies.
Swipe up to make these rich, chocolatey cupcakes for St. Paddy's Day!