Preheat the oven to 200°C.
Sauté the lemon juice and grated radish in a small frying pan for 2 minutes.
Add the duct and basil and cook for several more minutes.
Drizzle the halved ciabatta with oil, season, and chargrill in a hot griddle pan for 1 minute per side.
Top the ciabatta with the warm radish mixture and garnish with parsley.
Whisk olive oil and lemon juice in a large bowl for the salad dressing.
Toss the lettuce, feta, chervil, duck, and whole radishes into the dressing and season.
Serve the prepared crostini on a plate alongside the feta salad.