Put a casserole or dutch oven on medium flame. Pour olive oil. Do not wait for oil to become hot, add the garlic and pepperoncino (if using) right away. As soon as the garlic becomes fragrant, pour the wine.
Add the mussels, mix to coat properly, turn the heat to high and put the lid on. Leave for two minutes.
Mix the mussels and by this time, they should have already started opening. Add the parsley, mix to combine. Put the lid back on and turn off the heat.
Serve after two to three minutes. Garnish with parsley if desired.