Trim lamb and dice into bite-size pieces. Combine the spice mix ingredients and divide in half.
In a heavy-based casserole, heat 1 tablespoon of the oil over high heat, add the lamb and half the spices and season to taste. Cook, stirring, until browned all over. Transfer lamb to a plate and drain any fat from pan.
Heat the remaining oil and spices in the same pan over medium heat until aromatic, about 20-30 seconds. Add the onion, leek and carrots and cook until onion is softened. Return the meat to the pan with the stock, raisins and tomatoes and stir well. Cover pan, reduce heat to low and simmer for 1 hour.
Add pear and simmer, uncovered, for 20-30 minutes or until lamb is tender and the sauce is thick. Stir occasionally and add extra stock or water if necessary.
Spoon tagine over the hot couscous, sprinkle with the almonds and serve.