Fill a tankard, beer glass or champagne flute half-way with champagne.
Pour an equal amount of stout beer into the glass.
Serve immediately.
Notes
Chill the stout and champagne the day before making your cocktail.
The amount of cocktails will depend on the size of glasses that are used.
To store leftover champagne: replace the cork with a silicone stopper, place the cage on top of the stopper and twist to secure. Store in the refrigerator.
Use leftover champagne or prosecco within a day or two.