Using a sharp knife slit the skin on the lamb shanks. Heat the oil in a thick bottomed pot and seal the lamb all around until meat is nicely browned, season with salt and pepper. Remove the shanks from the pot and any excess fat and stir in the chopped vegetables, except the pumpkin. Stir in the spices and cook for a minute or two (this will help to release all the aromas and flavours) Put the lamb shanks back into the pan, along with the lemon zest and the tomato paste. Cook the ingredients together for further 5 minutes. Next, pour in the stock and bring to the boil and then reduce the heat to a simmering point. Add the pumpkin, cover with a lid and continue cooking preferably in a hot oven for approximately an hour. Meanwhile, you can prepare the vegetables and the potatoes. To prepare the vegetables, place the 2 squares of baking paper on a tray. Slice the lemon into thin slices and put in the center of the paper squares, Top up with the thyme and ginger. Next, place on the vegetables and season well with salt and pepper. Drizzle with olive oil and wrap up the baking paper into tight parcels. Cook the vegetable parcels for about 25 minutes in a hot oven. At the same time, prepare the potatoes. Peel the potatoes and slice very thinly. Melt the butter in a thick bottom pan and sauté the garlic. Add the potatoes and stir well to glaze with the garlic butter. Pour in the liquids and season with salt, pepper and nutmeg. Reduce the heat and simmer for 5 minutes. Transfer the potatoes into an oven-proof dish and sprinkle over the Parmesan cheese and chopped parsley. Continue to cook the potatoes for 20 minutes in a moderate oven until golden brown. Finally, serve the Moroccan style lamb with the garlicky potatoes and the bag of cooked vegetables on the side.