Melt the butter or heat the oil in a large, deep pot. Combine the lamb, onion, coriander, peppers, cinnamon and salt and stir into the pot. Puree, or mash, the potatoes and toss them in. Meanwhile, thinly sliced potato, carrot, zucchini, and celery. When the meat is well browned, add 6-8 cups of water and bring to a boil. Toss in the sliced vegetables and the chickpeas. Cover, reduce heat to simmer and cook until everything is tender. Add water as necessary to make the amount of soup you need. A few minutes before serving, return mixture to a boil and stir in the pasta. Taste to see if you should shake in a bit more coriander, salt or pepper. When the noodles are cooked, serve in bowls with a slice of lemon floating on top.