Begin by seasoning each lamb shank generously with salt and pepper on all sides.

Heat half of the olive oil in a large skillet over medium-high heat. Sear each lamb shank for approximately 5 minutes, ensuring a nice sear on all sides. Once seared, transfer them to a plate.

Prepare the garlic by smashing the cloves, discarding the skins, and slicing the garlic into slivers. Using a knife, create small slits in the lamb and insert the slivers of garlic into the meat.

In a mixing bowl, combine potatoes, cheese (such as Feta, Graviera, or Kasseri), onions, tomatoes, oregano, paprika, olive oil, any leftover garlic slivers, and lemon juice. Make sure to season the mixture generously with salt and pepper. Toss to coat the ingredients thoroughly and set the bowl aside.

Fold the parchment paper flaps toward the center, then twist and secure the paper to create a sealed parcel. Use a piece of string or twine to secure the parcels. Place the secured parcels on a baking sheet for cooking.

Preheat your oven to 350°F (175°C). Roast the parcels for approximately 1½ to 2 hours or until the lamb becomes tender.

Once done, remove the kleftiko parcels from the oven, and carefully cut the tops of the parchment paper to slightly open them. Baste the lamb with the flavorful juices from within the parcels.

Increase the oven temperature to 400°F (200°C) and roast for an additional 10-15 minutes to achieve a golden-brown finish on the lamb and vegetables.

Take the parcels out of the oven and cut off the tops of the parchment paper. You can serve the lamb and vegetables directly in the parchment paper or transfer them to a serving platter.

If you prefer, you can use a leg of lamb, cut into portions. Additionally, you have the option to use goat or pork instead of lamb.

As an alternative cooking method, you can prepare lamb kleftiko in a covered casserole dish by combining all the ingredients in one place. Adjust the cooking time based on the quantity of lamb used. In this case, parchment paper is not needed.