Two options, because the Irish are all about freedom...
The go-to in these Irish cocktails is always the Black Velvet – which double as an epic hangover cure for those whose intention is to prep their internal system for another round of day-drinking.
It’s easy enough and doesn’t tax the mathematical ability of the average hung-over Bond-daddy: Who can splice basis points while wildly drunk, but can’t handle a 2.5 to 1 ratio the next morning.
Take a champagne flute which, if the wife hasn't left you should be in the silver closet. If she has, don't stand on ceremony and just grab another glass. Fill half with Guinness stour and half with champagne. Think of it as a Peaky Blinder’s Mimosa.
Don't worry to much about the brand of Champagne, it won't be recognizable when you're done.
The problem is that the Black Velvet actually an English creation. Not British, but English – the unfortunate Ying to Ireland’s ill-advised Yang. It was actually invented at the Brooks Club in London, and you don’t get more establishment than that. It was 1861, a year the English were extremely comfortable with themselves and their empire. And we all know how unfashionable colonialism is these days.
If you don’t want to go through that, give a simple quaff of Tullamore Dew … and just don’t worry about it.