Rinse the mussels and drain well.
Heat the olive oil in a wide pan.
Over medium heat, cook the chorizo in the hot oil until it has rendered fat and the oil in the pan has colored.
Add the chopped onion to the chorizo and cook, stirring often, until softened.
Throw in the tomatoes, garlic and parsley. Stir. Set the heat to medium-low, cover the pan and cook the vegetables until they are just started to liquefy.
Turn up the heat to medium-high. Pour in the ginger ale. Allow to reduce by a quarter. Taste and add as much as salt as is needed to get a pleasant balance between salty and sweet.
Pour the mussels into the pan. Stir. Cover the pan and let the mussels cook for about five minutes or just until the shells open.
Serve the mussels and chorizo in ginger ale hot.