A Hemingway is a cocktail, in the loosest possible sense of the word. Although it's named after Ernest Hemingway, it's unlikely he ever went near this awful concoction.
To make an authentic Hemingway, absinthe is mixed with with champagne. If you can't find absinthe, Pernod can be substituted. If you don't have any champagne, you could probably use sparkling white wine. Basically, it's going to be a uniquely interesting experience whatever you use.
To make: Get a half pint or highball glass. Put two shots of absinthe or Pernod in it. Fill the glass with ice cubes, then fill it right to the top with champagne. Remove any sharp objects from your person, write the address of your house on your forehead, and kiss the rest of the evening goodbye.
When the champagne hits the absinthe, the drink will go an interesting yellowy-green color. Drinking it will achieve roughly the same effect as injecting grain alcohol directly into your eyeball.
There are all sorts of variations on the theme. The champagne can be combined with whiskey, schnapps, gin, grappa or anything similar in place of Pernod.