Also, I recommend using the Guinness Draught from the can as opposed to Guinness Extra Stout in the bottle. You will have better results . . . basically because the bottled version is meant to be drank straight from the bottle and not poured (see this blog post for more information)
It's interesting to note that you can have two distinctly different drinking experiences with this cocktail. You can float the Guinness much like is done with a Black and Tan. Or, you can mix it all together with a gentle stir. Either way is good . . . just different.
Guinness Cream Soda
2 Ounces Ginger Liqueur
2 Ounces Vanilla Liqueur
1 (12-ounce) Can Club Soda, Chilled
1 (14.9-ounce) Can Guinness Draught, Chilled
Combine the liqueurs in a cocktail shaker filled with ice. Shake to chill then mix with club soda, stir gently to combine.
Fill a chilled pint glass halfway with the club soda mixture.
If floating the Guinness, hold a spoon over the glass, slowly pour the Guinness over the back of the spoon until the glass is full.
Otherwise combine half the club soda mixture with half the can of Guinness. Stir gently if.
Makes two cocktails