Heat pan over medium high heat. Add oil, garlic and thinly sliced red onion, then mussels. Arrange mussels in a single layer. Add vermouth to the pan and cover. Cook until mussels open. Discard any unopened shells. Transfer mussels to a bowl. Pour juice over mussels and sprinkle with parsley, salt and pepper. You'll need a second bowl, for shells.
Recipe courtesy of Rachael Ray