Reserve the cooking liquor and keep the mussels warm. In the same pan, melt the butter and gently cook the shallot, ham and garlic for 4-5 minutes, until softened but not browned. Add the mussel ...

and any mussels that don't close tightly when you tap them. Heat the olive oil in a heavy pan with a tight-fitting lid. Add the shallot and garlic and cook over a medium heat until softened ...