Preheat oven to 180 C

Grease 24-30 cupcake cups and fill with paper cups

In a saucepan, heat the butter, Guinness, cocoa and brown sugar, whisking often, until the butter is melted and the mixture is smooth. Remove from the heat and allow to cool to room temperature.

Into a large bowl, sift dry ingredients and white sugar. Add the cooled Guinness mixture and beat on medium for 1 minute.

Add eggs and sour cream and beat on medium for 2 minutes

Divide the batter evenly between the cupcakes. Bake for 20-25 minutes, cool in pan for 20 minutes then transfer to a cooling rack

For the icing, cream the butter until light and fluffy. Slowly add icing sugar one spoon at a time. Add Bailey's and milk until spreadable consistency is achieved

Frost cupcakes when they are cool