Tortilla Espanola is a dish I make all the time at home. My boyfriend's family are Spanish, and he just loves this authentic dish. It's easy to prepare and always a crowd pleaser. Traditionally this dish only uses only onions, potatoes and egg; however I like to add a little green, either parsley or chives depending on your taste. They're both wonderful.
You can use chives instead of parsley, and a sweet red onion instead of the Spanish onion -- the sweeter, the better.