Rinse the lentils and transfer them to a saucepan.
Cover with cold water or broth.
Add bay leaf, garlic clove and onion.
Bring to a boil, reduce heat and simmer for 20 minutes.
Drain and transfer the lentils to a serving dish.
Place a pinch of salt in a bowl and add the wine vinegar, mustard and black pepper.
Pour in the olive oil and whisk.
Add grated horseradish.
Pour the vinaigrette over the salad and add the flat-leaf parsley.
Toss and then sprinkle the Parmesan shavings over the salad.
Serve the lentil salad as an appetizer or as an accompaniment to leftover cold cuts.