Finely chop the onions. Wash and stem the celery, remove the stems if necessary and cut into 1 cm wide pieces. Clean and peel the carrots, cut the thickest ones in half lengthwise. Cut the leeks in half lengthwise, wash and cut the white and light green parts into 5 mm wide pieces. Drain the salted lemon, cut it into thin slices and chop finely. Finely chop the parsley with the stems.
Heat 4 tablespoons of oil in a large saucepan. Sauté the onions, carrots, celery and leeks over medium heat for 2-3 minutes. Stir in the harissa and ducca and sauté briefly. Add the salted lemon pieces and the lentils. Fill with stock and 400 ml of water, briefly bring to the boil. Add cinnamon stick and parsley and cook uncovered over medium-high heat for 40 minutes, stirring occasionally.
Meanwhile, wash the pears, the quarter, the core and cut them into 1 cm cubes. Bring the white wine, 3-4 tablespoons water, sugar and rosemary to a boil in a saucepan. Cook uncovered over medium-high heat for 6 to 8 minutes, until most of the liquid has evaporated. Put aside.
Cut the skin off the duck breasts and cut them finely. Fry in the remaining oil (1 tablespoon) in a skillet over medium heat until crispy. Remove and drain on absorbent paper. Season the duck breasts on both sides with salt and pepper. Fry in the hot duck fat in a skillet over medium heat for 5 minutes on each side. Cut the meat into large chunks and add to the stew.
Mix yogurt in a small bowl until smooth and sprinkle with lemon zest, chili flakes, black cumin and Ducca.
Salt and pepper the lentil blanquette, sprinkle with mint leaves and a few diced pears and a crispy duck skin. Serve with spiced yoghurt and the rest of the duck skin and the rest of the diced pears.