Prepare the Lamb Shanks
Season lamb shanks generously with salt and pepper.
Preheat oven to 350°F.
Heat olive oil in a large Dutch oven over medium-high heat. Sear lamb shanks on all sides until deeply browned. Remove and set aside.
Add pearl onions and celery to the pot. Cook for 5 to 7 minutes until softened and lightly browned.
Stir in garlic and cook for 1 to 2 minutes until fragrant.
Add oregano, paprika, garlic powder, allspice, cinnamon sticks, salt, pepper, and bay leaves. Stir to combine.
Pour in red wine and scrape up any browned bits from the bottom of the pot. Simmer for 3 to 4 minutes until slightly reduced.
Add chicken broth and tomato sauce. Stir well.
Return lamb shanks to the pot and bring to a gentle simmer.
Cover with a lid and bake for 1½ hours. Remove the lid and continue cooking for another 30 to 45 minutes until the lamb is fork-tender and falling off the bone.
Make the Mashed Potatoes
About 30 minutes before the lamb is finished, boil potatoes until soft and fork-tender. Drain well.
Rice or mash the potatoes.
In the same pot, melt butter with salt, pepper, milk, and cream cheese over low heat.
Stir potatoes back into the pot until creamy and smooth. Adjust seasoning and consistency as needed.
Serve
Spoon mashed potatoes onto plates or shallow bowls.
Top with lamb shanks and plenty of braising sauce.
Garnish with fresh parsley and serve warm.