RED LENTIL & CARROT SOUP WITH SAFFRON MUSSELS

To make crisp leek, trim white part of 1 medium leek; halve lengthways. Rinse well; pat dry. Cut leek into long, thin strips. Heat oil for shallow-frying in a medium saucepan; cook leek, in batches, until browned lightly and crisp. Remove from the pan with a slotted spoon; drain on paper towel.