Grate the yellow rind of the lemon and press out the lemon juice. Rinse the mussels under cold running water and tap them against the work surface. Remove mussels which do not open. Place the good mussels in basket 2 (joined to basket 3 if necessary). Sprinkle in half of the garlic together with 1 dessertspoon of parsley, dessertspoon of thyme and some lemon rind.
Set the timer to 12 minutes. Press start and steam the mussels until they have all opened. Steam the mussels 1-2 minutes longer if necessary.
In the meantime, use a food processor to make breadcrumbs from the slice of bread. Add the anchovy fillets together with 1 dessertspoon of lemon rind, 2 dessertspoons of lemon juice, the remaining herbs and the olive oil. Mix everything together to form a smooth sauce. If necessary, add a few drops of water to thin the salsa verde a little.
Divide the mussels between two warmed deep dishes and drizzle the salsa verde over them. Delicious with a mixed salad and French fries.