For the lamb tagine, wash and pat dry lamb, removing tendons if necessary. Peel onions and cut into wedges. Sear lamb in batches in a little hot clarified butter until hot all around. Place with onions in an unperforated cooking container, season with salt and ½ tsp each cinnamon, cumin, coriander and cayenne pepper. Pour in lamb stock, add bay leaf and cook lamb (at 100 °C for 35 minutes or at 120 °C for 17 minutes).
Meanwhile, peel carrots and cut into thick slices. Wash lemon while hot, rub dry and cut into eighths. Add both to lamb with dried plums and continue cooking until meat is tender (at 100 °C 20 minutes or at 120 °C 8 minutes).
Add couscous and cook until tender (at 100 °C 5 minutes or at 120 °C 2 minutes).
Meanwhile, lightly toast sesame seeds in a pan without fat. Peel and press garlic, mix with yogurt and sesame seeds and season with salt and a little lemon juice. Remove bay leaf from the tajine, season with salt and spices and serve with sesame yogurt.