Preheat the oven to 180°C (350°F) or set the air fryer to the same temperature.
Cut the chicory heads in half lengthways.
Place them in a baking tray and brush with half of the olive oil and balsamic vinegar.
Roast or air fry for 10–15 minutes, until tender and lightly caramelised.
In a mixing bowl, combine the lentils with the remaining olive oil and balsamic vinegar.
Season to taste with salt and pepper.
Cut the beetroots into small pieces and halve the cherry tomatoes.
Mix them into the lentil salad.
(Optional: Add a finely minced clove of garlic for extra flavour.)
Arrange the baked chicory halves on a serving plate.
Spoon over the lentil and vegetable mixture.
Top with sardines and scatter over the rocket or watercress.