Bring sugar to a boil over MED-HIGH heat, without stirring, until the sugar is deep golden brown. It takes about 5 to 10 minutes. Remove the pan from the heat and add the cream. Whisk until it is smooth. Let cool and transfer to a container. I like to use a squeeze bottle, it makes the decorating easier.

Add the Guinness and butter to a medium saucepan, bring to a simmer over MEDIUM heat. Add cocoa and whisk until smooth. Set aside and let cool.

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

Beat the eggs and sour cream in the bowl of an electric mixer.

Add the Guinness mixture and beat until combined.

Add the flour mixture and mix until just combined.

Beat the butter in the bowl of an electric mixer. Add 1 cup sugar, beat until combined, gradually add remaining sugar. Add the Baileys until the frosting is desired consistency. Add more Baileys or sugar, if needed.