Heat canola oil until rippling in a pressure cooker pot. Add shank, season with salt and pepper, and cook 1-2 minutes each side or until deep brown. Remove from pot; set aside briefly. In the same pot, melt butter and cook onions until soft. Add tomato paste and garlic and cook until fragrant. Add wine and reduce. Stir in carrots, mushrooms, beef stock, Worcestershire sauce, bay leaves, paprika. Return browned beef to pot, stir and cook for 35 minutes at high or 15lbs (7 kg) pressure. Perform a quick pressure release. In a small bowl whisk together potato starch and cold water. Mix slurry into stew while hot. Stir in parsley and season with salt and pepper. Keep warm.