Fill 2/3 or a pint glass or Champagne flute with Guiness. Top with your favorite Brut Champagne or Sparkling Wine and serve chilled.
Notes
*If you don't want to splurge for Champagne, I recommend using a Brut-style Cava in the $10-15 range, such as Freixenet. Although pint glasses are traditional, you can serve this cocktail in a Champagne flute to give it a more elegant feel.