What do you do with a double yolk?

If a recipe calls for one egg, and you get a double yolk, is it still considered one egg, or if a recipe calls for 2 eggs, and you get a double yolk on your first cracked egg, do you stop there, or crack the second one which would give you 3 yolks? (sorry if it sounds confusing, my friend recently said she cracked open 2 double yolkers in a row for the first time in her life, that just got me thinking...)