In large bowl - combine lamb, pepper, garlic, paprika, oregano, salt, cumin, brown sugar, cinnamon sticks, and 1/4 cup oil. Mix well to coat meat, then marinate from 30 minutes to overnight.
Using sauté setting, heat Instant Pot. Once hot add 1/4 cup olive oil and thoroughly brown lamb on all sides – making sure to render all the fat. Once browned, remove lamb shanks and set aside.
Add onions, carrots, bay leaves, and remaining marinade to the pot. Sauté until onions become translucent – about 5 minutes.
Add red wine to deglaze the pot - making sure to scrape all the bits stuck to the bottom. Return lamb to pot. Simmer to reduce by half - about 10 minutes.
Add stock. Lock lid and cook for 30 minutes at high pressure.
Once cook time is complete, allow pressure naturally release. Remove shanks and set aside.
Pour liquid through a fine mesh strainer and return to pot. Discard cooked ingredients. Separately in a small bowl, combine cornstarch and water, then add to pot.
Switch Instant Pot back to sauté setting and simmer until sauce reaches desired thickness. Return lamb to pot and let sit in sauce until ready to serve.
Serve lamb with polenta or mashed potatoes topped with gravy!